The US Justice Department is launching an investigation based on President Donald Trump's unsubstantiated claims of widespread voter fraud in the US election. But the top prosecutor who would have the job of overseeing the investigation has quit in protest. A memo from Attorney General William Barr authorising the inquiry prompted Richard Pilger, head of the Justice Department’s elections crime branch, to resign. Mr Pilger told his colleagues that Mr Barr had implemented “an important new policy abrogating the 40-year-old non-interference policy for ballot fraud investigations in the period prior to elections becoming certified and uncontested", CNN reported. States oversee their own ballot counting and election certification process without federal involvement. The full certification process typically takes days or weeks after election day to complete. President Donald Trump is still refusing to concede the election after losing to Joe Biden, the president-elect. Mr Trump has justified his refusal to accept the election results with unsubstantiated claims of widespread voter fraud. Mr Barr’s memorandum on Monday acknowledged justice department guidelines stipulate “that overt investigative steps ordinarily should not be taken until the election in question has been concluded, its results certified, and all recounts and election contests concluded". But he said this was not “a hard and fast rule, and case-specific determinations and judgments must be made". Mr Barr’s request came shortly after he met Senate majority leader Mitch McConnell on Monday. Mr McConnell on Monday declined to acknowledge Mr Biden as the president-elect, instead backing Mr Trump’s mostly failed lawsuits against the election results. The Trump campaign and its allies filed lawsuits last week intended to stop the count of mostly postal ballots. And while the lawsuits have largely failed to advance and the ballot counting has continued, Mr Trump’s lawyers have threatened to increase their litigation. The Trump campaign is also calling for ballot recounts in states including Georgia, where no clear winner has yet to emerge because of a razor-thin vote margin as the count continues. The campaign also hopes to start a recount in Wisconsin, which Mr Biden won by more than 20,000 votes. But even if Mr Trump were to win Georgia and Wisconsin, he would not have enough votes in the electoral college for a second term in the White House. His refusal to concede the election has also delayed the already compressed timeline to transition between new administrations. US General Services Administration chief Emily Murphy has not signed the paperwork needed to start the taxpayer-funded transition process, despite Mr Biden’s victory. Mr Biden has already moved ahead with his transition planning, announcing a Covid-19 taskforce on Monday and giving more details of his strategy to fight the pandemic. The refusal of Mr Trump and his Cabinet to concede the election has not stopped world leaders from rushing to congratulate Mr Biden on his victory. UK Prime Minister Boris Johnson, Irish Taoiseach Micheal Martin, German Chancellor Angela Merkel and French President Emmanuel Macron all called Mr Biden to congratulate him on Tuesday. Meanwhile, Secretary of State Mike Pompeo declared Mr Trump the winner of the election. “There will be a smooth transition to a second Trump administration,” Mr Pompeo said when asked if he would work with Mr Biden’s transition team