Iran’s Foreign Minister Mohammad Javad Zarif has offered a swap for Anglo-Iranian political prisoner Nazanin Zaghari-Ratcliffe (pictured).

Zaghari-Ratcliffe, who worked for the Thomson Reuters Foundation charity, was seized in April 2016 as she and her infant daughter were leaving Tehran after visiting relatives. She was sentenced to five years for espionage, with no substantial evidence ever presented in the case.

Speaking at the Asia Society in New York on Wednesday, Zarif said he had the authority to arrange the swap, claiming it was offered in private six months ago to the US.

We have an Iranian lady in Australia who gave birth to a child in prison … after an extradition request by the United States because she was responsible as a translator in…a purchase of some transmission equipment for [an] Iranian broadcasting company.

Zarif’s statement is a significant shift of his position. He has previously said Zaghari-Ratcliffe’s detention is a matter for the Iranian judiciary.

Zaghari-Ratcliffe’s husband Richard Ratcliffe said he was unsure if Zarif was making l a serious proposal. He said he was “disoriented”: “Normally my sense with Iran is nothing is flippant, and so it will have a meaning, but it might not be the obvious meaning.”

Ratcliffe said the Iranians had mentioned a prisoner swap only once, in February 2017.

British Foreign Secretaries Boris Johnson and Jeremy Hunt have travelled to Iran seeking the charity worker’s release, but made no progress.

Earlier this year Zaghari-Ratcliffe and Iranian human rights activist Narges Mohammadi went on hunger strike over denial of medical care for serious conditions. They ended the strike after Iranian authorities allowed access to treatment.

A UK Foreign Office spokeswoman said:

The treatment of all British-Iranians detained in Iran, including Mrs Zaghari-Ratcliffe, is a priority for the government.

We remain concerned about all of our consular cases and raise them at every level and every opportunity.