Dual national Iranian-British charity worker Nazanin Zaghari-Ratcliffe returned to prison on Saturday evening after Iran's judiciary refused to extend her temporary release, her husband said.
The Free Nazanin campaign released images Thursday showing Zaghari-Ratcliffe hugging her 4-year-old daughter, Gabriella, during her release.
She has been in prison for more than two years on sedition charges, but was released from Evin prison on furlough on Thursday following campaigning from her family.
He is hoping she will be allowed to remain outside the jail for a couple of weeks, adding that her lawyer was "very confident" of an extension.
Foreign Secretary Jeremy Hunt urged Iranian authorities called on Iranian authorities to allow her to return to her family in the United Kingdom on Thursday. "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", Ratcliffe said.
Her husband had believed she would not have to go back into prison.
Responding to the news she had returned to jail, her local MP Tulip Sadiq tweeted: "Very sad to hear that Nazanin's extension was not granted, and she has been taken back into prison this evening".
Nazanin Zaghari-Ratcliffe, a project manager with the Thomson Reuters Foundation, was arrested in April 2016 at a Tehran airport as she was heading back to Britain with her two-year-old daughter after a family visit. The possibility of a temporary release had been discussed previously, but there had been a number of "false dawns".
The prosecutors office said she would need to return "for a few days or a week" to wait for a key signature, Mr Ratcliffe said.
Ratcliffe, who has been unable to get an Iranian visa, said his wife's temporary release had been both a good sign and a hard experience.
"We shouldn't lose sight of what Nazanin has had to endure - almost two-and-a-half years behind bars, eight gruelling months of solitary confinement without a lawyer, a deeply unfair trial, and also being subjected to a string of unfounded accusations from the Iranian authorities".