Judiciary spokesman Gholamhossein Esmaili said the female suspect had worked for the British Council and cooperated with British intelligence, trying to infiltrate in cultural field in Iran. He said the suspect had been jailed in Iran for the past year while her case was under investigation.
The British Council is a non-political organization that works in education, arts and culture.
Esmaili did not identify the suspect by name but said she had been studying in Britain and was recruited while looking for job there. He said the suspect was sentenced after "clearly confessing to assignments with the British intelligence." Before her detention, he said the unnamed suspect regularly visited Iran and had planned several cultural and artistic projects.
In a statement Monday, the British Council said it had seen reports of the sentencing but said "we have not been able to confirm that this is our colleague."
The British Council had released a statement earlier this month saying it was aware of the detention of a staffer following the arrest of Iranian national Aras Amiri. The council said she had traveled to Iran on a private trip to visit family, and not for work.
It was not immediately clear if Amiri was the woman sentenced Monday.
Britain's Foreign Office also released a statement saying it could not confirm more details and was "urgently seeking further information."
The sentencing comes at a time of increasing tensions between the U.S. and Iran over its unraveling nuclear deal with world powers. Though the British Embassy in Tehran has reopened, the British Council has been closed since 2009.
A British-Iranian woman held in Tehran, Nazanin Zaghari-Ratcliffe, is currently serving a five-year prison sentence for allegedly planning the "soft toppling" of Iran's government while traveling with her young daughter.
Zaghari-Ratcliffe, who works for the charity arm of Thomson Reuters, was arrested in April 2016. Her sentence has been widely criticized.
Iran does not recognize dual nationalities.
Many hardliners in Iran view the country as fighting a cultural "soft war" against westernization, which is attempting to transform the country's Islamic beliefs.