Nazanin Zaghari-Ratcliffe and her family are calling on the UN to again intervene in her case and highlight Iran's "abusive conduct".
Husband Richard is concerned that, despite rumours Iran was willing to release her, Nazanin's case has been "allowed to drift" and a window to get her home to West Hampstead has closed.
Nazanin was handed a further one-year sentence in April, having already served five years for charges of plotting to topple the Iranian government, something she has always denied.
The family's legal team has written to the UN, asking for its working group on arbitrary detention to "engage" with the authorities in both Iran and the UK about Nazanin.
It also wants the UN to intervene and offer a second comment on Nazanin's case, which would be unprecedented.
Lawyers from Redress and Doughty Street Chambers have asked the working group to comment on Nazanin's use as diplomatic leverage and acknowledge that her treatment is "tantamount to torture".
Richard Ratcliffe told this newspaper that this came on the back of a summer where "there's clearly been limbo".
He said that, having met Foreign Secretary Dominic Raab last week, along with the families of other Brits detained in Iran such as Anoosheh Ashoori and Mohrad Tahbaz, he is keen to ensure the UK government act to prevent that country "playing games".
In Iran, a new president, Ebrahim Raisi, was inaugurated on August 6. He is a hardliner who former political prisoners have said presided over thousands of extra-judicial executions in the late 1980s. Amnesty International has called for him to be investigated over crimes against humanity.
Richard said he fears that – with it appearing Nazanin's fate is now also tied to negotiations around the Iran Nuclear Deal – there is a risk of "ransom-creep".
He said: "We have always said we were a bargaining chip, and we are still a really visible bargaining chip."
On the submission to the UN, Richard added: "I met the foreign secretary this week to get his sense of things. He insisted the negotiations had come close, hoped they could be picked up again under the new regime, and that he was determined not to leave any Brits behind.
"I told him I feared the tide had turned, and that a summer of drift would become an Autumn in court.
"I see that now as inevitable, unless the UK and the international community takes a much firmer stand against state hostage taking, and calls it out as a crime.”
Richard said Nazanin, who is still awaiting details of her appeal against the second prison sentence and travel ban, is "up and down" as she remains trapped in Iran. She has been stuck there almost 2,000 days.
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"Speaking to Dominic Raab was a boost for her, I think. She's putting on a brave face for her mum and dad, but, for example, she has friends who are now back in solitary in prison and have Covid."
He continued: "My sense is that this could drift for a while yet, but I'm determined not to let this go on until Christmas."
Leanna Bernard, Redress's legal officer, said: "In the face of Iran’s flagrant violations of international law, diplomatic intervention at the highest levels is critical. After more than five years, Iran’s torture of
Nazanin must be stopped.”
The last fortnight saw the announcement that two further dual-nationals – British-Iranian Mehran Raoof, a teacher and trade unionist with ties to Islington, and German-Iranian Nahid Taghavi – were given 10-year jail sentences in Iran earlier this year.
Last Wednesday, Dominic Raab said Iran was at a “crossroads” with the inauguration of President Raisi. Mr Raab admitted in May that Nazanin was being held hostage.
He condemned Nazanin's continued detention of Ms Zaghari-Ratcliffe and also criticised a reported attack on an oil tanker in the Gulf of Oman which the UK believes was committed by Iran.
Richard Ratcliffe was concerned the new prison sentences and the tanker attack represent a change of tack from the new Iranian regime.
A government spokesperson said: “Iran’s continued arbitrary detention of our dual nationals is unacceptable. We urge the Iranian authorities to release the detainees without any further delay.”
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