The Foreign Office is following up the case of a British woman sentenced to 20 years in prison in Iran for allegedly criticising the country's leadership.
Roya Saberi Negad Nobakht, 47, from Stockport, was held while visiting friends in the city of Shiraz last October, the AFP news agency reported.
Cheadle MP Mark Hunter said the sentence was "draconian and appalling".
The Foreign and Commonwealth Office said it was following up the case with Iran.
AFP said an opposition website claims she was one of several people jailed for posting anti-regime propaganda on Facebook.
Mr Hunter, a Liberal Democrat, said the case was "very worrying" and it was a "very distressing time for all of Mrs Nobakht's family and friends".
"Given there are no diplomatic relations between Iran and Britain it is not easy or straightforward," he said.
He said Mrs Nobakht had British and Iranian nationality but this was not recognised by Iran and they were "treating her as one of their own".
Hazel Grove MP Andrew Stunell said the sentence was "outrageous" and he was working with Mr Hunter to get "a fair and proper outcome for the family".
The Foreign Office 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."