Nazanin Zaghari-Ratcliffe has been sentenced to another year in prison on charges of "propaganda activities against the regime" in Iran, according to reports.
The UK-Iranian national is also banned from leaving the country for one year for participating in a protest in front of the Iranian Embassy in London in 2009, her lawyer Hojjat Kermani told Emtedad news website.
"Nazanin Zaghari was sentenced to one year in prison and one year ban from leaving the country on charges of propaganda against the Islamic Republic," Mr Kermani told the website following the Iranian Revolutionary court’s ruling.
Prime Minister Boris Johnson told reporters on Monday he thought the sentencing was "wrong".
He said: "We will have to study the detail of what the Iranian authorities are saying.
"I don’t think it’s right at all that Nazanin should be sentenced to any more time in jail. I think that it was wrong.
"I think it’s wrong that she’s there in the first place and we’ll be working very hard to secure her release from Iran."
He added that the "government will not stop" and will "redouble our efforts" to fight for Mrs Zaghari-Ratcliffe’s release, and will work alongside "our American friends on this issue as well".
In March, the aid worker was released from house arrest and had her ankle tag removed after her five-year prison term expired.
But she was unable to return to the UK to be reunited with her husband and young daughter and was told to return to court on a new charge of "propaganda against Iran".
The 42-year-old was arrested at a Tehran airport while taking her infant daughter to see her parents in April 2016 and was later jailed over disputed allegations she was plotting to overthrow Iran’s government.
Her family and her employer, the Thomson Reuters Foundation, a charity, deny the allegation.
Richard Ratcliffe, her husband, previously described the latest court hearing as coming at the end of a "long ordeal" and said he would be "very surprised" if his wife was acquitted.
He added: "We have had some ups and downs – often on the same day."
State media in Iran have not immediately acknowledged the sentence.
It comes as Iran and Britain negotiate over a long legal dispute over an arms sale from the time of the shah.