Iran has made fresh allegations against jailed British-Iranian mother Nazanin Zaghari-Ratcliffe, including claims she set up a spy network.
The charity worker, who is serving five years in a Tehran prison, has been accused of recruiting for the banned BBC Persian service and "opposition cyber teams".
The new allegations were broadcast on Saturday night on Iranian state TV, hours after she called supporters taking part in a march to thank them.
It comes as the UK considers making a £400m payment to Iran, to clear an outstanding debt that Tehran says London owes.
Iranian state TV, which showed what it claimed were various documents that amounted to proof, said: "The BBC team in which Nazanin was a member designed, programmed and executed the Iran Project from 2007 for three years.
"According to this document, Nazanin had eight important duties in the fields of training and recruitment for the purpose of launching the BBC Persian service, espionage institutions and opposition cyber teams.
"Nazanin Zaghari cooperated with the BBC channel until 2010 but quit the BBC after the end of her project and joined a more serious project."
Mrs Zaghari-Ratcliffe was arrested in April 2016 while about to return from a holiday visiting relatives in Iran with her toddler daughter Gabriella. It was her fifth visit in 22 months.
The charges at her trial were kept secret but she has been accused of acting to undermine the regime in Tehran.
British Foreign Secretary Boris Johnson was blamed for putting her at risk of a longer sentence by saying she was in Iran to train journalists – something her family staunchly denies.
Her husband, Richard Ratcliffe has called on Mr Johnson to do more to win her release and to take him to Iran so he can see the wife and daughter he has been unable to see for the last 19 months.
The latest TV report was accompanied by images, which the station claimed was documentary evidence, of a BBC redundancy letter from 2010, a BBC payslip from 2010, a university letter from 2007, a 2010 email to a contact from Mrs Zaghari-Ratcliffe saying she worked for the BBC World Service Trust training journalists and a 2009 letter to the British Embassy in Iran saying she is a training assistant with the BBC World Service Trust.
It has been widely reported that Mrs Zaghari-Ratcliffe joined the Thomson Reuters Foundation in 2010 after leaving BBC Media Action, the corporation's international development charity, which was previously called the BBC World Service Trust.
The BBC's Persian TV service, which was initially funded by the Foreign Office, launched in 2009. It is said to be independent from government and is now funded by the BBC World Service from the licence fee
The service, which is widely watched via satellite in Iran and beyond, fell foul of the Iranian authorities after it reported on protests against the regime in late 2009.
The BBC and several other major western news organisations have reported that BBC Persian service and other foreign-based Iranian journalists and their families have been subjected to persecution by the Iranian regime.
Mr Ratcliffe reacted to the Iranian state TV report by saying it was designed to increase pressure on the British government.
London has said it may repay Tehran hundreds of millions of pounds it owes from a pre-1979 arms deal that did not go through, which has prompted critics to accuse the Government of paying a ransom – something the UK government refuses to do.
Both sides say any payment would not be related to Mrs Zaghari-Ratcliffe's case, even though a similar payment by America came as Iran released four US citizens in 2016.
On Saturday, Sky News witnessed Mrs Zaghari-Ratcliffe speaking by phone to her supporters from her jail at a rally in Hampstead, north London, at which she said she about her potential release: "I can't wait for that day".