Nazanin Zaghari-Ratcliffe 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 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 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.

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 BBC Radio 4’s Woman’s Hour.

Nazanin Zaghari-Ratcliffe meets PM
Nazanin Zaghari-Ratcliffe with her husband Richard Ratcliffe and daughter Gabriella as they leave 10 Downing Street, central London, after a meeting with Prime Minister Boris Johnson (Victoria Jones/PA)

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 a British official was present at the time she signed the document.

Mrs Zaghari-Ratcliffe and Anoosheh Ashoori arrive at Brize Norton after they was freed from detention by Iranian authorities in March
Ms Zaghari-Ratcliffe and Anoosheh Ashoori arrive at Brize Norton after they was freed from detention by Iranian authorities in March (PA)

“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.”

Tulip Siddiq, the Ratcliffes’ constituency MP in Hampstead and Kilburn, called for Liz Truss to answer the “serious questions” about Ms Zaghari-Ratcliffe’s treatment.

The Labour politician said: “The Foreign Secretary must set out in Parliament what she knew about this shocking revelation and what consequences it could have for my constituent.”

It was argued in the UK that the Iranian authorities insisted Ms Zaghari-Ratcliffe would not be able to leave unless she signed the form, and that the British official did not force her to sign it, only passing on Tehran’s demand.

A Government spokesman said: “Iran put Nazanin Zaghari-Ratcliffe through a horrendous ordeal, right up to the moment she left the country.

“Throughout that time the UK Government was working tirelessly to end her unfair detention, but it was always in Iran’s gift to release Nazanin and allow her to return to her family.

“We urge the Government of Iran to end its practice of unfairly detaining British and other foreign nationals, and we will continue to work with international partners to that end.”

Nazanin Zaghari-Ratcliffe meets PM
Ms Zaghari-Ratcliffe with her husband Richard Ratcliffe (Victoria Jones/PA)

Earlier this month, her 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.”

The Women’s Hour interview with Emma Barnett will be broadcast on BBC One at 8pm on Monday.