A British-US national temporarily freed from prison in Iran before being sent back to jail two days later has gone on hunger strike, his family says.
Morad Tahbaz, 66, who also has Iranian citizenship, has since been moved to a hotel, the Foreign Office has said.
His sister Taraneh told the BBC his family was “absolutely distraught” and feared he would be forgotten about.
The Foreign Office says it is continuing to lobby Iran at the highest levels for Mr Tahbaz to be released.
Hopes had been raised that Mr Tahbaz would be freed when Nazanin Zaghari-Ratcliffe and Anoosheh Ashoori were released and flew back to the UK on Thursday, but he was returned to Evin prison on Friday.
The Foreign Office said it had been informed by the Iranians this move was in order for Mr Tahbaz to have an electronic ankle bracelet fitted.
Speaking on the Today programme, Taraneh Tahbaz said the family does not know what is going on.
“[Morad] is in despair and we are in despair and we no longer know what else we can do…
“For four years we were led to believe that he would be part of the deal [which led to the release of Nazanin Zaghari-Ratcliffe and Anoosheh Ashoori]… and the deal was made, the money [for an historic UK debt to Iran] was paid, and he wasn’t part of the deal and he’s still there.
“We’re just very, very worried that all of this is just going to get swept under the rug.”
Mr Tahbaz was doing conservation work when he was held in Iran in January 2018.
He and seven other conservationists were accused of collecting classified information about Iran’s strategic areas under the pretext of carrying out environmental and scientific projects.
The conservationists – members of Persian Wildlife Heritage Foundation – had been using cameras to track endangered species including the Asiatic cheetah and Persian leopard, according to Amnesty International.
All eight denied the charges and Amnesty International said there was evidence that they had been subjected to torture in order to extract forced “confessions”.
He was sentenced to 10 years in prison with his colleagues on vague charges of spying for the US and undermining Iran’s security.
Last year, UN human rights experts warned that Mr Tahbaz, who has cancer and has twice had Covid, had been denied access to proper treatment in prison despite his health condition deteriorating.
- WHERE DID ROMAN ABRAMOVICH’S MONEY COME FROM? Panorama investigates the deals that made his fortune…
- THE INSTAGRAM EFFECT: What power does the platform hold over us?