Nazanin Zaghari-Ratcliffe has been summoned to court in Iran on Monday, according to her family, who said she has been told to pack a bag as she will be returned to prison following the hearing.
The 42-year-old mother-of-one, who has been detained in Iran since 2016, was moved to house arrest in March, when thousands of prisoners were granted clemency and released from Iranian jails amid the Covid-19 outbreak.
Her husband Richard Ratcliffe said in a statement: 'We don't know what will happen on Monday, we don't know how far and how soon they will take forward their prison threat.
Iranian-British aid worker Nazanin Zaghari-Ratcliffe is seen in an undated photograph handed out by her family
'But we do know that the Revolutionary Guard are signalling something to the British government. We also know they are signalling this could have a long time still to run.
'As Nazanin's husband, I do think that if she's not home for Christmas, there's every chance this could run for years.
'I really hope there's something we're not being told, as on the face of it the Government's response seems disastrous, just extraordinary that they won't change course.'
The news of Mrs Zaghari-Ratcliffe's imminent trial was revealed the same day it was announced that a court hearing about Britain's £400million historic debt to Iran had been postponed from 3 November this year to 20 April 2021.
Her lawyers accused Iran of 'holding Nazanin hostage' in relation to the debt and urged the UK government to respond with the 'strongest possible action'.
Mrs Zaghari-Ratcliffe's local MP Tulip Siddiq said the timing of the trial raised 'serious concerns'.
Before she was placed under house arrest, Nazanin was imprisoned at Iran's notorious Evin prison (pictured)
Iranian women inmates sit at their cell in the infamous Evin jail, north of Tehran, in 2006
The MP for Hampstead and Kilburn said in a statement: 'Nazanin has once again been treated with utter contempt and I am extremely concerned about her future and wellbeing.
'The fact that she has been told to pack a bag for prison ahead of her court hearing doesn't fill me with confidence that this will be anything close to a fair trial.
'The timing of this development alongside the postponement of the court hearing about the UK's historic debt to Iran raises serious concerns.
'I can only hope that there is work going on behind the scenes to resolve the debt quickly because we seem to be going in completely the wrong direction and Nazanin, as ever, is paying the price.
'The Foreign Secretary must assert the UK's right to consular access and ensure that UK officials are present at Nazanin's trial.'