Iran promised to provide better protection in future for diplomats and said there would be no repeat of the storming of the British embassy last week, which has damaged its already strained ties with Europe.
Britain shut its embassy, withdrew its diplomats and expelled Iranian diplomats from London after the attack, which saw protesters storm its embassy and a residential compound, smashing buildings and burning offices.
Other European countries, including France and Germany, also withdrew ambassadors from Tehran in solidarity with London.
London says the incident could not have happened without some official Iranian government support. Iran says it was the result of a spontaneous outpouring of anger after Britain imposed a new set of sanctions over its nuclear programme.
Asked in an interview if Iran could guarantee that diplomats will be better protected in future, Foreign Minister Ali Akbar Salehi said: Yes, this experience has immunised us against these kinds of illegal actions. This won't happen again.
In the interview, published on Tuesday in the German daily Frankfurter Allgemeine Zeitung, he denied that the government was behind the embassy storming: Why would we support such a thing? he asked.
He said he had expressed regret in a phone call with Foreign Secretary William Hague.
But I also explained the reasons of the attack to him, Salehi said. Britons angered the Iranian people with their stance.
Iran denies Western suspicion it is seeking atomic weapons and says its nuclear work is entirely peaceful. A report last month by the International Atomic Energy Agency watchdog, which suggested Iran is seeking a nuclear weapon, has prompted European countries and the United States to tighten sanctions.
The EU is considering banning imports of Iranian crude oil.
Tehran caused a stir on Sunday at conference on Afghanistan in Bonn when it said it had shot down a U.S. spy drone in its airspace and threatened to respond. NATO-led forces in Kabul said the drone may have been one lost last week while flying over western Afghanistan.
Asked about allegations by the West that Iran is backing Afghan rebels, Salehi joked: The next time there is a tsunami or an earthquake - the West will blame Iran for it. This is how the West thinks.
(Reporting By Natalia Drozdiak and Robin Pomeroy; Editing by Peter Graff)