A British-Iranian engineer detained in Tehran’s Evin jail tried to kill himself three times in solitary confinement after agents threatened to harm his British-based relatives unless he co-operated during 12-hour interrogation sessions, his family has said. During questioning inside a grim prison-within-a-prison controlled by the Islamic Revolutionary Guard Corps, interrogators told Anoosheh Ashoori, 66, that agents had tracked the movements of his family in London. They claimed to have logged the times that the family walked their pet dog and bought products from his daughter’s patisserie business in south-east London. His family believe the information was gleaned from social media accounts but the threats drove the retired engineer to take drastic action. “He concluded that: ‘I’m better off dead because at least I won’t pose a danger for them’,” his wife said. “They have an expression at Evin that they make you commit suicide. They drive you to that point.” The brutal treatment of Mr Ashoori, who has now served more than three years of his sentence, was detailed in the UK’s parliament this week. The treatment is likely to have been repeated with newly-detained dual nationals after their arrests on what their governments say are trumped-up charges. Iranian-American Emad Shargi was jailed for 10 years for spying in November last year, while a German woman, Nahid Taghavi, 66, was arrested in October and has been held in an IRGC section of the prison and endured periods of solitary confinement. The continuing detentions of dual-national prisoners present an early test for US President Joe Biden, who says that he wants to rejoin the deal to limit Tehran’s nuclear ambitions that was abandoned by his predecessor. Mr Ashoori, who is married with two children, was detained in August 2017 after travelling to Iran to visit his mother. He was convicted nearly a year later of spying for Israel’s intelligence agency Mossad. He was sentenced to serve 10 years in prison, in line with a pattern of long jail terms for dual nationals who critics say are later used as pawns of the regime for prisoner exchanges and other diplomatic horse-trading. His family believe his fate is tied to a decades-old £400 million debt owed by the UK following an aborted deal to sell tanks to the Shah of Iran. Delivery was halted after the 1979 revolution but the money was not repaid. Mr Ashoori was held for the first four months of his detention in solitary confinement where he was subjected to daily interrogation. As well as the suicide attempts, he also went on hunger strike for 17 days. “He was interrogated for up to 12 hours a day,” said Mrs Izadi. “He was being told if he doesn’t co-operate they will hurt us here in Britain. “They would give him details of our lives. He had no idea how they were able to get that information. “They [the IRGC] do a number on your head, really. That first few months is the most difficult time. “Any prisoner will tell you the same thing when they have no contact with family and with no idea of what’s happening.” Janet Daby, an opposition Labour Party MP, this week criticised the strategy of Boris Johnson for securing the release of British dual nationals held by Iran. Some of the families have not gone public but the UK is believed to have one of the highest numbers of Iranian-held dual nationals. “They are people being brutally mistreated over an international financial dispute,” said Ms Daby. “They are hostages. When will the Foreign Office accept that and acknowledge them as such? “Ultimately we need detailed assurances that the UK government will do all they can to support Anoosheh’s release from prison and to step up their efforts to bring him home.” Mr Ashoori has applied for conditional release after serving more than one-third of his sentence, but the prospects for his imminent release are considered low, with fellow British dual national Nazanin Zaghari-Ratcliffe being forced to remain in Iran to see out a five-year term, as well as the threat of another potential prosecution. James Cleverly, the UK's Middle East minster, told parliament that the government was working “flat out to secure Mr Ashoori’s full and permanent release”. “From the Prime Minister down, the government are clear that we do not accept British dual nationals being used as diplomatic leverage and that it is essential that they are released,” he said.