Former British-Iranian hostage Nazanin Zaghari-Ratcliffe says Iran forced her to sign a last-minute false confession at the airport before letting her board the plane as a UK Foreign Office official was witnessing.

Zaghari-Ratcliffe, who returned to London in March along with another dual national after Britain repaid a historic debt of £400 million, said on Monday that she signed the statement "under duress" as a condition of her release after about six years of imprisonment on trumped-up spying charges, expressing worries that Tehran would use the “confession” against her in the future.

Saying that the whole process of signing the forced confession was filmed, she said, “It’s a tool. So, I’m sure they will show that someday.”

She told the BBC that she was taken to the airport by the Iranian Revolutionary Guards without seeing her parents, adding, “Instead I was made to sign the forced confession at the airport in the presence of the British government”.

The former prisoner said she wanted to make sure people knew she had been forced to sign, to prevent the Iranian regime from exploiting her "dehumanizing" confession, which is “just propaganda for the Iranian regime to show how scary they are, and they can do whatever they want to do.”

Iran is holding several Western prisoners in what human rights organizations have dubbed hostage diplomacy, accusing the Islamic Republic of holding dual-nationals as bargaining chips for money or leverage in negotiations with the West, something Tehran denies.