Nazanin Zaghari-Ratcliffe who was detained for six years has revealed she was forced to sign a "false confession" in front of a UK Government witness before she was allowed to leave Iran.
The British-Iranian dual national has spoken out and said the act captured on camera by the Iranians was "dehumanising", and that she expects Tehran to use it against her in the future.
While "under duress", she said was forced to admit to the Iranians' allegations after they detained her for six years having accused her of spying, a charge she and the UK denied.
The charity worker said she was taken to the airport by the Revolutionary Guards without seeing her parents on the day in March when she was to be freed.
"Instead I was made to sign the forced confession at the airport in the presence of the British Government," Ms Zaghari-Ratcliffe told the BBC.
The Iranians told her the UK had now settled a historic £400 million debt dating to the 1970s.
"They told me that 'you won't be able to get on the plane'.
"And I knew that that was like a last minute game because I knew they were... They told me that they have been given the money," she said.
"So what is the point of making me sign a piece of paper which is incorrect? It's a false confession."
She told the BBC's Emma Barnett that a British official was present at the time she signed the document.
"The whole thing of me signing the forced confession was filmed," Ms Zaghari-Ratcliffe added.
"It's a tool. So I'm sure they will show that some day."
Labour MP Tulip Siddiq has voiced her support for Ms Zaghari-Ratcliffe and vowed to find out why she was made to sign a confession "under duress".
"The Foreign Secretary must set out in Parliament what she knew about this shocking revelation and what consequences it could have for my constituent," she said on Twitter.
Earlier this month, husband Richard Ratcliffe alluded to "mistakes made at the end" of the ordeal in Iran.
Speaking after his wife's first meeting with Prime Minister Boris Johnson since her release, Mr Ratcliffe said: "I think there are lessons to learn, there is a wider problem.
"We talked about the mistakes made at the end.
"It was rough at the end, and I think, when Nazanin is ready to talk about it, that is something that we need to go through."
* ‘Nazanin Zaghari-Ratcliffe talks to Emma Barnett’ is on BBC One today at 8pm.
An extended version of the interview will be available on BBC Sounds from 8.30pm and on BBC Radio 4’s Woman’s Hour tomorrow at 10am.
