The attacks on the British embassy in Tehran were "a grave violation" of international conventions, Foreign Secretary William Hague has said.
Mr Hague said it was "fanciful" to think they could have taken place "without some degree of regime consent".
Hundreds of protesters massed outside the embassy compound on Tuesday afternoon before scaling the walls and the gates, burning British flags and a car. Another UK diplomatic compound in northern Tehran, known locally as Qolhak Garden, was also overrun and damaged.
In a statement to the Commons on 30 November 2011 the foreign secretary confirmed he had phoned the Iranian foreign minister "to protest in the strongest terms" against the attacks.
He said he had requested the closure of the Iranian embassy in London, but denied this represented a total severance of relations between the two countries.
Mr Hague warned it would be a "serious mistake" for Iran to think it could persuade the UK to back down from playing a leading role on the international stage, by intimidating embassy staff.
Shadow foreign secretary Douglas Alexander offered Labour's "clear unequivocal condemnation" of the "deplorable attack".
He said the Iranian government had failed to take adequate measures to protect the embassy and its staff, adding that it "stretches incredulity" that the regime, or elements of it, were unaware of the "co-ordinated" demonstrations.
Mr Alexander echoed Mr Hague's tributes to the British ambassador and his team as events unfolded.
Liberal Democrat Martin Horwood joined in condemning the attacks.
He asked whether support from countries such as Russia and China suggested "the beginnings of a foundation of a more consistent international approach to the regime in Tehran?".
Mr Hague said it was too early to say, but added: "I think this well help to open the eyes of many people across the whole world to the nature and behaviour of the Iranian regime, because if they have so little regard for such well established international conventions as the protection of diplomatic premises, then one can imagine they don't have much regard for other international agreements either."
Former Foreign Secretary David Miliband urged condemnations of Iran not to lead to a "drumbeat of war". William Hague responded by saying the UK was not advocating military action in Iran.
Britain is withdrawing some of its diplomatic staff from Iran following the attacks.
Iran said it regretted the incident, which it described as "unacceptable behaviour by a small number of protesters".