The husband of jailed British-Iranian mother Nazanin Zaghari-Ratcliffe has urged Boris Johnson to raise his wife’s case when he meets Iran’s foreign minister later.
Mrs Zaghari-Ratcliffe, 39, is serving a five-year jail sentence in Iran after being convicted of spying.
But Richard Ratcliffe says his wife is facing possible new charges.
Foreign Secretary Mr Johnson is due to meet his Iranian counterpart in Brussels for Iran nuclear deal talks.
British-Iranian dual national Mrs Zaghari-Ratcliffe, from Hampstead, north London, has been held in Iran since April 2016, when she was detained at an airport while travelling home with her daughter.
She was accused by Iran of plotting against the government. She denies the charges against her and says she was in the country to introduce her daughter, Gabriella, to her parents.
According to her husband, who released a statement via the Free Nazanin campaign on Tuesday, prosecutors have said that the case against her has been reopened.
The news of possible new charges against Mrs Zaghari-Ratcliffe comes as Mr Johnson prepares to meet his Iranian counterpart, Javad Zarif, in Brussels to discuss how to save the Iran nuclear deal after the US withdrew last week.
They will also meet the French and German foreign ministers and EU high representative Federica Mogherini.
Mr Ratcliffe said his wife’s case and the cases of other dual nationals detained in Iran should be “top of [Mr Johnson’s] priority list” at the meeting.
He said the UK “needs to do better by British Iranians” and is “failing to protect them”.
There are nearly 30 dual nationals being held by the Iranian authorities – many of whom are accused of security offences.
On Sunday, Prime Minister Theresa May urged Iran’s president to make further progress over the release of British-Iranians “on humanitarian grounds”.
In November last year, Mr Johnson apologised for telling a Commons committee hearing that Mrs Zaghari-Ratcliffe had been teaching journalism in Iran – something her family and employer say is incorrect.