British-Iranian charity worker Nazanin Zaghari-Ratcliffe appeared in court in Iran's capital Tehran on charges of spreading propaganda against the regime.
Zaghari-Ratcliffe's lawyer said the charges were based on her participation in a protest outside the Iranian embassy in London 12 years ago, and her involvement in an interview with the BBC's Persian news service.
Zaghari-Ratcliffe was jailed in 2016 for "plotting to topple the Iranian government", an allegation which she has consistently denied.
The UK-Iran dual national was released after five years on 17 March 2020 and then freed from house arrest on 7 March 2021.
She has not been allowed to leave Iran due to the new charges, a situation the British Prime Minister Boris Johnson previously described as "totally unacceptable".
In a tweet, UK Foreign Secretary Dominic Raab said it was "unacceptable" that Iran had chosen to continue with the second "wholly arbitrary" case, and that she must be allowed to return to her family in the UK without delay.
Richard Ratcliffe, who attended a Free Nazanin rally in London on Sunday, said the British embassy in Tehran had declined to accompany his wife to the trial.
Zaghari-Ratcliffe's family fears the Iranian government wants to detain her for longer for diplomatic leverage.