LONDON (AP) — A British-Iranian charity worker who was detained in Tehran for almost six years says she was forced by Iranian officials to sign a false confession to spying before she was freed two months ago.

Nazanin Zaghari-Ratcliffe said British government officials were present at Tehran airport when “under duress” she signed the false admission to spying. She said she was told by Iranian officials that “you won’t be able to get on the plane” unless she signed.

“The whole thing of me signing the forced confession was filmed,” Zaghari-Ratcliffe told the BBC in an interview broadcast Monday. “It’s a tool. So I’m sure they will show that some day.”

Opposition Labour Party lawmaker Tulip Siddiq, who represents Zaghari-Ratcliffe’s home district in London, said the revelation raised “serious questions” for the British government. She said Foreign Secretary Liz Truss “must set out in Parliament what she knew about this shocking revelation and what consequences it could have for my constituent.”

Zaghari-Ratcliffe was detained at Tehran’s airport in April 2016 as she was returning home to Britain after visiting family in Iran. She was employed by the Thomson Reuters Foundation, the charitable arm of the news agency, but she was on vacation at the time of her arrest.

Zaghari-Ratcliffe was sentenced to five years in prison after she was convicted of plotting the overthrow of Iran’s government, a charge that she, her supporters and rights groups denied. She had been under house arrest at her parents’ home in Tehran for the last two years.

She and another dual citizen, Anoosheh Ashoori, were released and flown back to the U.K. in March. Their release came after Britain paid a 400 million pound ($503 million) debt to Iran stemming from a dispute over tanks that were ordered in the 1970s but were never delivered.