The husband of an imprisoned British-Iranian woman has spoken of her anguish at being released from jail for three days before being forced to go back.
Nazanin Zaghari-Ratcliffe was taken to a prison clinic after passing out following her return to prison in Tehran last weekend.
Her husband Richard has written to Iran's foreign minister, saying the whole incident had been "a cruel game".
Middle East minister Alistair Burt is in Iran for talks about her case.
He has met Iran's deputy foreign affairs minister, Abbas Araghchi, in Tehran as well as speaking to Ms Zaghari-Ratcliffe's family.
During her temporary release, she was reunited with her family including her four-year-old daughter Gabriella.
'Cast a shadow'
Since returning to prison, she suffered several panic attacks and low blood pressure, her husband has said.
She was jailed for five years in 2016 after being convicted of spying, which she denies, saying she was on holiday to introduce her daughter to relatives.
Foreign Secretary Jeremy Hunt has promised to increase efforts to secure her release.
In his open letter to Javad Zarif, Mr Ratcliffe described the week of her release and return to prison as "a tough one" which led her to wish she had never been allowed to leave jail, adding: "At the end, we felt held together by Sellotape."
He described how an Iranian official had contacted his wife's father, warning him to ensure no one from the British Embassy should visit her during her temporary release "if she wanted to stay safe".
"Each day he called to note they were monitoring her movements, and check her father was following her to make sure she did not suffer an accident on the street. Those calls cast a shadow over her release, as they were meant to," he wrote.
"Nazanin called me on Tuesday - one of our toughest conversations.
"She wished she had never been released. She said she felt like one of the radical Islamists' captives - as though she had been paraded on the balcony then hidden back away."
The first of two panic attacks came after that phone call, he said.
Mr Ratcliffe wants Mr Zarif to meet him next week at the United Nations General Assembly in New York to discuss his wife's imprisonment.
Mr Burt will discuss the case of several British dual-nationals detained in Iran, as well as holding talks on the Iran nuclear deal and conflicts in Syria and Yemen, during his visit.
He said, before the trip, he would "use the opportunity of my visit to push for the resolution we all want to see in the cases of the British dual-nationals detained in Iran".