Britain has closed its embassy in Iran and all UK staff have left the country after the compound was stormed by protesters, Foreign Secretary William Hague has revealed.
He announced that the Government was also requiring the closure of the Iranian embassy in London and the departure from Britain of all of its staff within the next 48 hours.
Addressing the Commons, Mr Hague said Tehran should be "ashamed" of the events that took place on Tuesday.
About 24 embassy staff and their dependants were based at the embassy's office and residential compounds in Tehran.
In a statement to the Commons, Mr Hague said the last of those staff had departed from Iran.
He said the attack on the embassy was conducted by about 200 demonstrators from an organisation "controlled by elements of the Iranian regime".
Iran's failure to protect British diplomatic staff was a breach of the Vienna Convention and "for which any nation should be ashamed".
Relations between Britain and Iran, already difficult, have worsened in recent weeks amid renewed concerns about president Mahmoud Ahmadinejad's nuclear ambitions. But Mr Hague insisted: "No difficulty in relations can ever excuse in any way or under any circumstances the failure to protect diplomatic staff and diplomatic premises."
He said he had called the Iranian Foreign Minister, who had said he was "sorry for what had happened".
He urged against all but essential travel to Iran and said British citizens in need of help would be able to get consular assistance from other EU missions in Tehran.
