Mr Johnson told the audience a Labour government would increase taxes and would not stand up to Russian President Vladimir Putin.
“They will scrap the Rwanda plan,” he said before describing Labour MPs as “Kremlin crawlers”.
Mr Johnson criticised Mr Starmer for not being able to explain “the difference between a man and a woman”.
“He sits there with his mouth open like a stunned mullet,” he said.
Boris Johnson's time as British Prime Minister - in pictures
Boris Johnson became UK prime minister in July 2019, left, and resigned three years later in July 2022, right. Here 'The National' looks back at his colourful time as leader of the country. Getty Images / Reuters
Boris Johnson reads a statement outside 10 Downing Street, formally resigning as Conservative Party leader. PA
Boris Johnson and his wife Carrie Johnson attend the National Service of Thanksgiving to celebrate the Platinum Jubilee of Queen Elizabeth at St Paul's Cathedral in June 2022. Getty Images
Boris Johnson addresses the media after surviving a confidence vote in his leadership, in June 2022. PA
Sir Graham Brady, chairman of the 1922 Committee of Tory backbenchers, announcing that Mr Johnson had survived a confidence vote in his leadership at the Houses of Parliament in June. PA
Mr Johnson chats with residents in a Diamond Jubilee-themed room as he makes a constituency visit to Sweetcroft care home in Uxbridge, in May 2022. Getty Images
Boris Johnson reads the findings of the Sue Gray report into gatherings on government premises while Covid-19 restrictions were in place, in his office in No 10, Downing Street in May 2022. Photo: Downing Street
An image of a gathering in the Cabinet Room in No 10, Downing Street in June 2020 on the prime minister's birthday was released alongside the Sue Gray report. Photo: Cabinet Office
Boris Johnson with a Mark 3 shoulder launch missile system at Thales weapons manufacturer during a visit to Northern Ireland for talks, in May 2022 in Belfast. Getty Images
Mr Johnson having a turban placed on his head at Gujarat Bio Technology University, during his two-day trip to India in April. Getty Images
Mr Johnson after apologising to MPs for the 'partygate' fine he had received, in the House of Commons in April. AFP
Mr Johnson and Ukrainian President Volodymyr Zelenskyy walking in central Kyiv, in April. AFP
Mr Johnson arrives for a media interview at the Emirates Palace hotel in Abu Dhabi, in March 2022. Getty Images
Mr Johnson speaks with officers as he makes a constituency visit to Uxbridge police station in December 2021. Getty Images
Mr Johnson observes an early morning Merseyside Police raid on a home in Liverpool as part of 'Operation Toxic' to infiltrate county lines drug dealings in December 2021. Getty Images
Boris Johnson during a visit to Westport Care Home in Stepney Green, ahead of unveiling his long-awaited plan to fix the social care system, in September 2021. Getty Images
Prince Charles looks on as Boris Johnson attempts to open his umbrella at the National Memorial Arboretum in Stafford, in July 2021. Getty Images
President of the European Council Charles Michel, US President Joe Biden, Japanese Prime Minister Yoshihide Suga, Mr Johnson and Italian PM Mario Draghi pose for the leaders' official photo during the G7 summit in Cornwall, in June 2021. Getty Images
Mr Johnson poses with his wife Carrie in the garden of No 10, Downing Street following their wedding at Westminster Cathedral, in May 2021. Getty Images
Mr Johnson visits Hartlepool after the Conservative Party candidate Jill Mortimer won the Hartlepool by-election in May 2021. Getty Images
Mr Johnson receives his first dose of the AstraZeneca vaccine at St. Thomas' Hospital in London, in March 2021. Getty Images
Mr Johnson smiles during a televised press conference at No 10, Downing Street in February 2021, as he announces a phased exit from the country's lockdown measures. Getty Images
Mr Johnson gives a thumbs-up gesture after signing the Brexit trade deal with the EU in No 10, Downing Street, in December 2020. Getty Images
Mr Johnson and European Commission President Ursula von der Leyen meet for a dinner to try to reach a breakthrough on a post-Brexit trade deal, in December 2020 in Brussels. Getty Images
Mr Johnson with a vial of the AstraZeneca Covid-19 candidate vaccine, known as AZD1222, at Wockhardt's pharmaceutical manufacturing facility, in November 2020, in Wrexham, Wales. Getty Images
Mr Johnson drills during his visit to Exeter College in September 2020. Getty Images
Mr Johnson holds crabs caught on the Carvela at Stromness Harbour in July 2020, during a visit to Scotland. Getty Images
Mr Johnson holds a painting of a ladybird during a visit to The Discovery School in West Malling, in July 2020. Getty Images
Mr Johnson and his fiancée Carrie Symonds applaud for key workers outside No 10, Downing Street, in May 2020. Getty Images
Boris Johnson appears on monitors for a meeting in London. The prime minister chaired the morning update meeting remotely as he was self-isolating after testing positive for
Covid-19. Reuters
Boris Johnson makes a televised address to the nation from inside No 10, Downing Street, with the latest instructions to stay at home to help contain the Covid-19 pandemic, in March 2020. AFP
Mr Johnson attends the launch of the UK-hosted COP26 Summit at the Science Museum in London, in February 2020. Getty Images
Mr Johnson is greeted by staff at No 10, Downing Street, after meeting Queen Elizabeth II and accepting her invitation to form a new government in December 2019. PA
Mr Johnson and his partner Carrie enter Downing Street as the Conservatives celebrate a sweeping election victory in December 2019. Getty Images
Mr Johnson drives a digger with the words 'Get Brexit Done' inside the digger bucket through a fake wall emblazoned with the word 'GRIDLOCK', during a general election campaign event in December 2019. Getty Images
Mr Johnson eats pie on the campaign bus in Derby, on the final day of campaigning before the general election in December 2019. Getty Images
Mr Johnson takes a turn in goal during the warm up before a girls' football match between Hazel Grove United JFC and Poynton Juniors in December 2019. Getty Images
Mr Johnson poses with workers as he is given a tour of Wilton Engineering Services as part of an election campaign trail stop in November 2019, in Middlesbrough. Getty Images
Mr Johnson poses for a photo wearing boxing gloves during a stop on his general election campaign trail in Manchester, in November 2019. Getty Images
Mr Johnson eats a rock sweet which reads 'Back Boris' during a general election campaign trail stop in Blackpool, in November 2019. Getty Images
Mr Johnson leads a bull around a pen as he visits Darnford Farm near Aberdeen, Scotland, in September 2019. Getty Images
Former US president Donald Trump and Mr Johnson arrive for a bilateral meeting during the G7 summit in August 2019, in Biarritz, France. Getty Images
Queen Elizabeth welcomes Mr Johnson as the newly elected leader of the Conservative party and invites him to become prime minister and form a new government, at Buckingham Palace in July 2019. Getty Images
Mr Johnson said the Labour Party's expected landslide win must be curbed.
“They can achieve nothing in this election except to usher in the most left-wing Labour government since the war with a huge majority, and we must not let it happen," he told campaigners.
“Don’t let the Putinistas deliver the Corbynistas. Don’t let Putin’s pet parrots give this entire country psittacosis – which is a disease you get, by the way, from cosying up to pet parrots.
“Friends, if you actually – everybody if you actually want higher taxes next week, this year, if you feel you’ve got a few thousands to spare, then vote Labour on Thursday.
"If you want uncontrolled immigration and mandatory wokery, and pointless kowtowing to Brussels again, then go right ahead, make my day, vote for Starmer.
“But if you want to protect our democracy and our economy and keep this country strong abroad by spending 2.5 per cent of our GDP on defence, which Labour still refuses to commit to, then you know what to do, don’t you, everybody?
“There’s only one thing to do – vote Conservative on Thursday, my friends, and I know you will. I know you will.”
Mr Sunak followed Mr Johnson's speech by saying voters must “think about what a government with a blank cheque would do.
“Just think, just think, it was just the other day when Keir Starmer was saying that Jeremy Corbyn would have been a better prime minister than Boris," he said.
“Shameful. Can you imagine what that would have meant for Ukraine? What it would have meant for our country’s security, our defence, the damage it would have done to our economy?”
Closing his speech from a podium set up underneath a suspended military helicopter, Mr Sunak said: “Do not surrender to Labour … fight for every vote”.
“I love my country,” he told the cheering crowd. "My story would not be possible in any other country.”
A number of people came forward to shake hands with Mr Sunak as the lights faded and he headed for the exit.
Starmer and Sunak in last-ditch pleas to voters as campaign enters final day
On Tuesday evening Mr Sunak and Labour Party leader Mr Starmer made their last-ditch pleas to voters as the British general election campaign entered its final 24 hours.
Mr Sunak is again urging wavering voters to stick with the Conservative Party, to stop a Labour “supermajority” in the House of Commons.
In one final speech in Hampshire on Wednesday, he will claim that Tory MPs will help to offer a balance to what is expected to be a landslide majority for Labour.
In a bid to dissuade the public away from other rival parties, Mr Sunak will also warn a vote for the Liberal Democrats would help to secure a Labour victory, as they will back the party's ideas in the next Parliament.
He said that Reform UK is likely to win only a handful of seats.
Mr Sunak is also expected to bring up disputed claim that Labour’s proposals for government will lead to a £2,094 ($3,684) rise in taxes for the average household.
“Only we Conservatives can stand up to Labour," he will say, according to early released excerpts from his speech.
Fourteen years of Conservative Party rule - in pictures
David Cameron, the new Prime Minister, and his wife Samantha enter No 10 Downing Street after his meeting with Queen Elizabeth II in May 2010. All photos: Getty Images unless otherwise stated
Theresa May speaks outside No 10 in July 2016 after assuming office as Prime Minister
New PM Boris Johnson is welcomed by staff at Downing Street on July 24, 2019
Liz Truss poses with her husband Hugh O'Leary at Downing Street on September 6, 2022 after becoming Prime Minister
Rishi Sunak speaks at Downing after taking office on October 25, 2022
Mr Cameron and Deputy Prime Minister Nick Clegg of the Liberal Democrats hold their first joint press conference in the Downing Street garden in May 2010. The Conservatives and Liberal Democrats agreed to lead the country in a coalition government
Barack Obama and Mr Cameron play table tennis at the Globe Academy in south London during the US President's state visit to Britain in May 2011
Mr Cameron talks to British soldiers during a visit to the Camp Price forward operating base in Helmand Province, Afghanistan, in December 2012
Mr Cameron attends a meeting of G7 leaders in March 2014 in The Hague, Netherlands
Afghanistan's President Ashraf Ghani and Mr Cameron speak to the media during the London Conference on Afghanistan in December 2014
Mr Cameron and his wife Samantha are applauded by staff upon entering 10 Downing Street as he begins his second term as Prime Minister in May 2015
Mr Cameron travels on his campaign bus on the final day of campaigning in June 2016 as the country prepares to go to the polls to decide whether Britain should remain or leave the European Union
Mr Cameron resigns on the steps of 10 Downing Street on June 24, 2016, after the UK voted to leave the European Union in the national referendum
Queen Elizabeth welcomes Ms May to an audience where she invited the former home secretary to become Prime Minister and form a new government in July 2016
Ms May signs the official letter to European Council President Donald Tusk invoking Article 50 and the United Kingdom's intention to leave the EU, in March 2017
Ms May delivers a speech during an election campaign visit to Stoke-on-Trent in June 2017, before Britain went to the polls to vote in a general election
Ms May delivers a statement at Downing Street in November 2018, after the cabinet approved the wording of the draft Brexit agreement for UK withdrawal from the European Union on March 29, 2019
Ms May announces that she will resign as Prime Minister on June 7, 2019
Mr Johnson waves from the door of 10 Downing Street on July 24, 2019
Mr Johnson poses for a photo wearing boxing gloves emblazoned with 'Get Brexit Done' during a stop in his general election campaign trail in November 2019
Pro Brexit supporters celebrate at Parliament Square as the United Kingdom exits the EU on January 31, 2020
Mr Johnson speaks during a news conference on the Covid-19 pandemic in December 2020
Chief Advisor to Mr Johnson, Dominic Cummings, makes a statement at 10 Downing Street in May 2020 after travelling to Durham during the coronavirus lockdown
A handout photo released as the Sue Gray Report into lockdown parties in Downing Street was published, shows Mr Johnson at a gathering there in November 2020
Mr Johnson poses in a group photo during the G7 Summit in Carbis Bay, Cornwall, in June 2021
British armed forces work with the US military to evacuate
eligible civilians and their families out of Kabul, Afghanistan, in August 2021, after the Taliban took control of the country
Russian military vehicles crossing a Crimea border checkpoint into Ukraine in February 2022 as the Russian invasion of Ukraine begins. AFP
Ukrainian President Volodymyr Zelenskyy and Mr Johnson look at a plaque dedicated to Johnson in Kyiv in August 2022
A man stands on the steps of the grounded Rwanda deportation flight EC-LZO Boeing 767 at Boscombe Down Air Base, in June 2022. The flight taking asylum seekers from the UK to Rwanda was grounded at the last minute after the intervention of the European Court of Human Rights
Mr Johnson addresses the nation as he announces his resignation outside 10 Downing Street in July 2022
Mr Sunak and Ms Truss take part in a leadership debate in Stoke-on-Trent in July 2022
Queen Elizabeth greets the newly elected leader of the Conservative Party Ms Truss at Balmoral Castle for an audience where she was invited to become Prime Minister in September 2022
Ms Truss and Chancellor Kwasi Kwarteng visit Northfleet in September 2022, as the Chancellor released his 'mini-budget' that included tax cuts and sent sterling to a 37-year low
Ms Truss delivers her resignation speech at Downing Street in October 2022, after just 44 days in office
New Conservative Party leader and incoming Prime Minister Mr Sunak is greeted by colleagues at party headquarters in London in October 2022
Mr Sunak on board Border Agency cutter HMC Seeker during a visit to Dover in June 2023, as he gave an update six months after he introduced the Illegal Migration Bill under his plans to "stop the boats" crossing the English Channel
Mr Sunak makes a statement in the pouring rain, as he called a general election, in May this year
“So, if you are one of those 130,000 voters who could stop a Labour supermajority, lend us your support, for we are the only party that can stop a supermajority and stand up to Labour.”
“If you are worried about an unchecked, unaccountable Labour government you can stop that by offering us your support so we can stand up for you and be your voice in the next Parliament.
“Your vote will determine whether your MP is just another addition to Starmer’s supermajority or a local champion, someone who cares about you and will fight for your area and its needs.
“Do you want a member of Parliament who holds the government to account or one who just unthinkingly backs Keir Starmer and whatever he wants to do?
“With your vote, you have the power to ensure that Keir Starmer doesn’t have a blank cheque, that there are MPs there to hold him to account.”
Poll after poll are now suggesting the Labour Party is expected to win a large majority in Parliament.
An average of all polls completed during the seven days to July 2 puts Labour on 40 per cent, 19 points ahead of the Conservatives on 21 per cent, followed by Reform on 16 per cent, the Lib Dems on 11 per cent and the Greens on 6 per cent.
Analysis by The Times of YouGov polling has suggested Labour has a broad voter coalition in many areas, but that support is sometimes not deeply held.
The newspaper has said this means if only 130,000 people switch their votes on polling day, it could drastically reduce the predicted majority of Mr Starmer’s party.
Britain's Labour Party through the years - in pictures
Deputy Labour leader Angela Rayner, and Labour leader Keir Starmer meet party supporters in Harlow in May. All photos: Getty Images
London Mayor and Labour incumbent Sadiq Khan, and his wife Saadiya Khan, pose with supporters after Mr Khan was re-elected in May
Mr Starmer meets and greets supporters in Chatham in 2023
Then-party leader Jeremy Corbyn during a 2017 visit to Oxford
First minister of Scotland Nicola Sturgeon, left, and leader of Scottish Labour Kezia Dugdale place roses at a memorial for murdered Labour MP Jo Cox, in Glasgow in 2016
Labour leader Ed Miliband, sixth right, holds his first shadow cabinet meeting at the House of Commons in 2010
Newly elected Labour prime minister Tony Blair stands on the steps of No 10 Downing Street with his wife Cherie in 1997
Mr Blair, John Prescott and Gordon Brown at the Labour Party Conference in 1997
Former leader Neil Kinnock, left, shares a joke with Peter Mandelson, a key figure behind the party's 1997 general election landslide victory, at the party conference in 1997
Leader John Smith addresses a miners' rally in Hyde Park, London, in 1992
Mr Kinnock with a group of youngsters publicising Labour's jobs And industry campaign in 1985
BBC TV coverage of the October 1974 general election, with Labour prime minister Harold Wilson and his wife Mary visible on a screen in London
Mr Wilson, left, and Labour politician Tony Benn speaking at a press conference during the 1974 general election campaign
Barbara Castle speaking at the Labour Party Conference in 1969
Mr Wilson waving outside No 10 in 1964
Mr Wilson, left, with deputy leader George Brown in 1963
A campaign poster issued by the Labour Party depicting leader Hugh Gaitskell arm-in-arm with Barbara Castle and Aneurin Bevan in 1959
Party leader Clement Attlee with a Labour delegation, boarding a plane on their way to China in 1954
Mr Attlee and his wife Violet attending a film premiere in London in 1952
Members of the Labour cabinet at No 10 in 1929: Clockwise from top left: Tom Shaw, Arthur Greenwood, Noel Buxton, Sidney Webb, Arthur Henderson and prime minister Ramsay MacDonald
Mr MacDonald addressing a Labour victory meeting at the Royal Albert Hall, London, in 1924
From left, Mr Henderson, William Brace, William Adamson, Vernon Hartshorn and James Henry Thomas outside Unity House during a coal workers' strike, in London, 1920
Scottish Labour politician James Keir Hardie addressing a peace meeting in Trafalgar Square, London, in 1914
Mr Hardie speaks at a tailors' rally on May Day in Hyde Park, London, in 1912
Mr Starmer will conclude a whirlwind tour of the country on Wednesday in a final bid to secure Labour’s return to power after 14 years.
In Staffordshire on Tuesday, he issued one last rallying cry to activists, saying: “Let’s get this over the line, let’s get that Labour government.”
As the election approached, Labour’s national campaign co-ordinator Pat McFadden said voters faced a “big choice” on Thursday, between “five more years of chaos with the Conservatives or change with Labour”.
“Don’t forget: one rule for them, another for everyone else," Mr McFadden said.
"Don’t forget the economic chaos for which the British people are still paying the price. Don’t forget the cronyism.
“You can put a stop to it. Change is in your hands and you can be part of it.”
Mr Starmer and his shadow cabinet are expected to spend Wednesday crossing the country, selling Labour’s six “first steps” and urging voters not to “risk” five more years of Conservative government.
Despite Labour’s consistent poll leads, he has sought to avoid sounding complacent, stressing that polls do not always “predict the future”.
But Mr Starmer's campaign stops in the final week have suggested ambitious targets, as he visited seats with Conservative majorities of more than 10,000 votes.
“We’re out in constituencies where we haven’t necessarily won before, because we think that many people are disillusioned with what they’ve seen in the last 14 years," he told reporters.
“We’re a changed Labour Party and we’re constantly putting our case forward, still smiling, still with a spring in our step that we’re probably the only positive campaign left now.”