The health of jailed conservationist Morad Tahbaz has been deteriorating daily since he was left languishing in an Iranian jail after the collapse of a deal to secure his release in March, his daughter said on Wednesday. Mr Tahbaz, 66, who holds British, US and Iranian citizenship, was returned to prison after several days of freedom in Tehran as two other British-Iranians, <a href="https://www.thenationalnews.com/world/uk-news/2022/05/24/uk-complicit-in-nazanin-zaghari-ratcliffes-false-confession/" target="_blank">Nazanin Zaghari-Ratcliffe</a> and <a href="https://www.thenationalnews.com/world/uk-news/2022/03/31/anoosheh-ashoori-paranoia-pain-and-fighting-back-in-irans-evin-jail/" target="_blank">Anoosheh Ashoori</a>, were flown home to the UK after years of detention. Mr Tahbaz was not supposed to be returned to prison as part of a deal after the UK paid back a £400 million ($500) debt from an aborted arms deal dating back to the 1970s — but Iran reneged on its side of the bargain. His eldest daughter Roxanne Tahbaz told the BBC that her father had cancer before he was detained that required regular monitoring and treatment. “But he's in prison, so we have no way of knowing what state any of his health issues are in,” she said. “It's been nine weeks now and my father is still not out of the prison. Every day that passes, he's deteriorating. He's got health issues. “He doesn't know everything that we're doing but all he knows is that he was left there. And he's still sitting in prison.” Mr Tahbaz was a founder of the Persian Wildlife Heritage Foundation, which seeks to protect endangered species in Iran. He was arrested on charges of spying for the US and undermining Iranian security, along with other members of the group in January 2018 and sentenced to jail for a decade. He was temporarily released in March to be with his wife — who is subject to a travel ban — in Tehran but did not fly back to the UK as was hoped with the other former detainees. Ms Tahbaz said Britain’s Foreign Ministry had repeatedly assured the family that all the detainees would be treated the same. Mehran Raoof, another British-Iranian and a labour rights activist, also remains in prison in Iran. Ms Tahbaz was speaking a day after Ms Zaghari-Ratcliffe, 43, told of her anguish that Mr Tahbaz had not return to Britain with them. “I cannot begin to tell you how I felt that day when I realised that Morad was not on the flight,” she told the BBC. “I was mortified. I just could not believe that he was left behind.”