A new charge against Nazanin Zaghari-Ratcliffe, the British-Iranian woman jailed in Iran, is “a new stage in an long-running political game”, her husband Richard has claimed.
“She is clearly being held as a bargaining chip,” Mr Ratcliffe said.
Mrs Zaghari-Ratcliffe is nearing the end of her sentence for spying charges, which she denies. But on Tuesday, she was told she would face a new trial.
The Foreign Office said British officials will try to attend the trial.
Mrs Zaghari-Ratcliffe was arrested in Tehran in April 2016. She had been visiting her parents with her young British-born daughter, Gabriella, who is now six.
The dual national was sentenced to five years in prison over allegations of plotting against the Iranian government – although no official charges have ever been made public.
Gabriella has now returned to the UK.
Earlier this year, Mrs Zaghari-Ratcliffe was given temporary leave from prison because of the coronavirus outbreak and has been living at her parents’ house in Tehran with an ankle tag.
But on Tuesday, she was told she will face another trial, which will be held on Sunday.
The new charge had not previously been publicly disclosed, but Mr Ratcliffe said it was an allegation of “spreading propaganda against the regime”.
“Her lawyer got to look at the file,” he told BBC Radio 4 Today programme. “It looks like the file is really a rehash of what she got convicted of first time round.
“But, you know, previously the evidence has changed between the lawyer reading it and what happens in the court case so we’ll only really know on Sunday what she’s going to be accused of.”
Mr Ratcliffe told BBC Radio 4 that the news was “certainly very tough for her”, adding: “I spoke to her just before she went into court.
“That’s probably when she was most terrified and in all honesty she had fears that she was being taken back to prison, not to court at all, it was a big trick.”
“She’s been really counting down the days until the end of her sentence and suddenly those goalposts look like they are about to move,” he added to BBC Breakfast.
Mr Ratcliffe said his wife and other dual nationals are being held hostage because Iran wants the UK to pay a decades-old debt over an arms deal that was never fulfilled.
The UK owes Iran about £400m for some Chieftain tanks it promised the former Shah of Iran but never delivered after the 1979 revolution.
The UK has agreed to pay the money but can’t until a legal way is found to get round the sanctions that currently make repayment impossible.
“Behind closed doors I’ve been warning the government that the closer we got to the end of her sentence without things being sorted, the more there was a risk of something happening, and so it’s come to pass,” said Mr Ratcliffe.
“This is definitely political, and it’s definitely a new stage in an long-running political game.”
He said: “The UK needs to take a much firmer line to protecting its citizens. It did invoke diplomatic protection more than a year ago – it hasn’t done very much with it.”
Mrs Zaghari-Ratcliffe’s family and the UK government have always maintained her innocence and she has been given diplomatic protection by the Foreign Office – meaning the case is treated as a formal, legal dispute between Britain and Iran.
The Foreign, Commonwealth & Development Office said that British officials will seek to attend any new hearings in Iran against Mrs Zaghari-Ratcliffe.
They said in a statement: “Iran bringing new charges against Nazanin Zaghari-Ratcliffe is indefensible and unacceptable.
“We have been consistently clear that she must not be returned to prison.”