The Iranian ambassador has been told of the UK's "grave concern" at a move to bring fresh court proceedings against Nazanin Zaghari-Ratcliffe.
The British-Iranian, under house arrest in Tehran since being moved from jail in March, has been summoned to court next Monday and told to expect to return to prison, her husband has said.
The charity worker is nearing the end of her current five-year sentence after being jailed on spying charges in 2016.
She has always denied the charges.
Iranian Ambassador Hamid Baeidinejad was summoned to the Foreign Office on Thursday, where Thomas Drew, Foreign Office director general for the Middle East, conveyed the UK's "grave concern" at Ms Zaghari-Ratcliffe being recalled to court, a department spokesman said.
In the meeting Mr Drew also called for Iran to end her "arbitrary detention", the spokesman added.
"We have made it clear to the Iranian ambassador that his country's treatment of Nazanin Zaghari-Ratcliffe is unjustified and unacceptable, and is causing an enormous amount of distress," the spokesman said.
"Iran is further tarnishing its reputation through its actions towards Nazanin.
"It is time to end her arbitrary detention and that of the other dual British nationals it is holding."
Mrs Zaghari-Ratcliffe, 42, was arrested in April 2016 while travelling to visit her parents with her young British-born daughter, Gabriella.
The dual national was sentenced to five years in prison over allegations of plotting to overthrow the Iranian government, which she denies. Prior to her arrest, she lived in London with her husband, Richard Ratcliffe, and child.
She was allowed to leave prison in March due to the coronavirus pandemic but remains under house arrest.
In September, she was told she would face a new trial, only months from her expected release date.
Mr Ratcliffe said it would hear charges of spreading anti-government propaganda.
This case was previously dropped by officials in December 2017, after a visit from the then foreign secretary Boris Johnson, but was reopened in May 2018.
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.
Mr Ratcliffe believes 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.