A British man who went to Iran in search of his missing wife discovered her languishing in prison at the start of an enormous 20-year sentence.

Roya Nobakht, 47, has been jailed for a Facebook post she published while on holiday in the country. It offended hard-line Muslim leaders by bashing former supreme leader Ayatollah Khomeini.

Stockport resident Nobakht – who holds dual British/Iranian citizenships, fell foul of strict religious laws and was convicted of putting Iran's national security at risk and insulting Islam.

Husband Doryoush Taghipoor only found out about his wife's plight when she failed to show up at Manchester Airport last October. He flew to Iran to find her, scouring places such as hospitals. Since he tracked her down, the couple have spent only 10 minutes together.

Nobakht has been tortured while in captivity, alleged a relative, who said: "Roya is devastated. She is not doing well. She has said she would trather die then be there for 20 years. She has been tortured and the conditions in prison are terrible."

The authorities sent Nobakht to the notorious Evin prison in north-west Tehran, a mixed facility that has been described as the country's toughest jail.

A Foreign Office spokesman said: "We are aware that a British national has received a custodial sentence in Iran."