The Foreign Office said Saturday it was following up the case of a British woman reportedly sentenced to 20 years in jail in Iran for posting anti-regime propaganda on Facebook.
Iranian opposition website Kaleme said Roya Saberinejad Nobakht, an Iranian-born British woman, was among eight people jailed for posts on the social networking site.
The 47-year-old, from Stockport outside Manchester in northwest England, was detained whilst visiting friends in the city of Shiraz in October, reports said.
Nobakht has dual British and Iranian nationality and has lived in England with her British husband, Daryoush Taghipoor, 47, for more than six years, according to The Times newspaper.
He travelled to Iran to find her, was allowed to visit her for 10 minutes and has not seen her since, the daily said.
A Foreign Office spokeswoman said: "We are aware that a British national has received a custodial sentence in Iran. We are seeking to establish the full facts and are following up the case with the Iranian authorities."
There is an ongoing clash in Iran between moderates, backed by President Hassan Rouhani, and hardliners, over Internet freedom.