The British Foreign Office says it is investigating newspaper reports that one of the UK embassy workers detained in Iran has been formally charged, BBC reported.

The Guardian says the embassy's chief political analyst has been accused of "acting against national security."

On Friday, a top cleric said some staff members would be tried for inciting protests over Iran's disputed election.

Iran says the UK is trying to undermine the Islamic regime by fomenting discontent - a charge Britain denies.

Foreign Secretary David Miliband says he is "deeply concerned" and has asked for talks with his Iranian counterpart.