Charity worker Nazanin Zaghari-Ratcliffe has not been granted an extension to her temporary release from imprisonment in Iran and has returned to Evin prison, her husband, Richard Ratcliffe, has said.
The British-Iranian mother was released from the Tehran jail on Thursday and had been staying with family outside the capital.
Mr Ratcliffe said that earlier on Sunday, his wife had visited the deputy prosecutor in a bid to try and have her furlough extended.
Initially she was told that an extension of her leave had been granted and she returned to her parents' house, yet 10 minutes after her return, she received a phone call telling her that she would have to return to prison by 7pm on Sunday (3.30pm BST).
Mr Ratcliffe added that a "shivering, shaking and crying" Ms Zaghari-Ratcliffe returned to the prosecutor's office with her daughter, Gabriella, to plead her case, only to be told: "If you do not go back when told, they will come to get you."
He continued: "After discussion with her family in Iran, Nazanin decided that she would go into prison.
"She did not want to be dragged out of the house in front of her baby, but would walk into prison with her head held high."
In response to the news that Ms Zaghari-Ratcliffe has once again been imprisoned, Foreign Secretary Jeremy Hunt said the "Iranian legal system is impervious to the simple fact at the heart of this: an innocent woman is desperate to be reunited with her family".
Mr Hunt added that he had spoken to his Iranian counterpart, Mohammad Javad Zarif, on Friday in a bid to have the London mother's leave extended, but this "clearly wasn’t enough".
In response to the news that she must return to prison, Ms Zaghari-Ratcliffe said: "This feels a dark world.
"I used to pray - but these past two years I've lost much of my faith.
"Who would take a child from their mother?
"I was so happy yesterday walking in the street seeing normal life again, but I also envied the people in the street yesterday walking holding their children's hands.
"I just want a normal life....
"How can I survive tonight - with those tears of my baby, pouting and crying, and telling me she doesn't want me to go back?
"She is adorable, and she is also kind and caring.
I couldn't bear her tears. Nothing is worse than her tears. I cannot forget her face."
While in a message to her husband in the early hours of this morning, Ms Zaghari-Ratcliffe spoke of her fears that she would be made to return to Evin on Sunday.
“I really need to sleep, but I am worried to death as I don’t know what happens tomorrow - whether I will still have the chance to sleep next to my baby and hear her breath as I can now, or whether I will be in that prison away from her again," Ms Zaghari-Ratcliffe said.
"The thought of going back really kills me - even before tomorrow comes."
Mr Ratcliffe branded his wife's return to Evin "an extraordinary decision. I did not believe after all the effort it took to get out, it would only be for three days."
He added that the British Embassy had already been told that his wife would have to return to prison when Ms Zaghari-Ratcliffe's family contacted them.
Following the news that Ms Zaghari-Ratcliffe must return to prison, the Foreign Office said it does “not think it is in the best interests of any of our dual national detainees to provide a running commentary on individual cases...
“We remain very concerned about all our dual nationals detained in Iran, and continue to make decisions in line with what we believe will produce the best outcomes in their cases."
It had been hoped that the 39-year-old's leave would be extended, since many of her cellmates who had previously been granted furlough had had their leave extended to more than a month.
Mrs Zaghari-Ratcliffe was first arrested in Iran as she attempted to leave the country in 2016.
She was imprisoned for five years on charges of spreading propaganda, but her family maintain she was in the country on a holiday.
In November 2017, her case achieved new prominence after former foreign secretary Boris Johnson appeared to tell a parliamentary committee that Mrs Zaghari-Ratcliffe was in Iran training journalists - something the Iranian authorities accused her of, but which she denied.
Mr Johnson later acknowledged he had misspoken.
It was further compounded by remarks made by Environment Secretary Michael Gove, who said he did not know why she was in Iran.