Nazanin Zaghari-Ratcliffe said she was forced to sign a letter of false confession in front of a UK government witness before she was allowed to leave Iran.
While “under duress” the 44-year-old mother of one, said she had 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.
Speaking to the BBC’s Emma Barnett for Woman’s Hour, she described how she was filmed on camera by the Iranians and expects Tehran to use it against her in the future.
The West Hampstead charity worker said she was taken to the airport by the Iranian 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,” she told the BBC.
“Why would I sign something? I have been trying very, very hard for the past six years to say I have not done it.
"All the false confessions that we have been exposed to, they have no value.
"They are just propaganda for the Iranian regime to show how scary they are and they can do whatever they want to do."
She was sentenced to five years for plotting to overthrow the Iranian government, and then sentenced to another year for propaganda against Iran in 2021.
She was released alongside fellow British-Iranian detainee Anoosheh Ashoori in March, after the UK government repaid a historic £400 million debt to Iran.
Earlier this month her husband Richard Ratcliffe hinted at “mistakes being made at the end.”
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 and Mr Johnson met for the first time earlier this month since, the Prime Minister wrongly claimed in 2017 that she had been training journalists at the time of her arrest in 2016.
Mrs Zaghari-Ratcliffe asked Mr Johnson why it took so long to get her home and told him his "mistake" had left a "lasting impact".
She also used the meeting with the Prime Minister to urge him to use his influence to secure the release of other British citizens still held hostage in Iran.