Britain's foreign ministry has told Iran's charge d'affaires that comments by Iran's supreme leader, in which he accused the UK government of being among the "most treacherous" of Western powers, are "unacceptable".
Iran's ambassador to the UK was summoned to the foreign ministry in London on Friday to explain the remarks made by
Ayatollah Ali Khamenei earlier in the day, but the charge d'affaires attended in his place.
During a sermon in Tehran, Khamenei said Western nations were showing "their enmity against the Islamic Republic system and the most evil of them is the British government".
He criticised foreign powers for questioning the result of Iran's presidential election, after Mahmoud Ahmadinejad, the incumbent, was declared to have won with an overwhelming majority.
A British foreign ministry spokesman said: "We made clear to the Iranian charge that the supreme leader's comments were unacceptable and not based in fact."
Speaking to Al Jazeera, Hamid Dabashi, a professor of Iranian studies at Columbia University in New York, said: "He [Khamenei] is using Britain metaphorically because of the history of British interference in Iranian affairs, the most significant of which was their involvement in the coup of 1953.
"It is for Iran now to show the world that the elections have been fair ... that the repression and the brutality that we have seen in these last few days is not something that is going to be repeated"
British prime minister
"But he is also using it in reference to the BBC, and BBC in Persian in particular. Iranians inside Iran are turning to the BBC, among other things, to see what is happening."
The BBC has accused the Iranian government of blocking the broadcast of its Farsi-language news service in the country.
Gordon Brown, Britain's prime minister, said during a European Union summit in Brussels on Friday that "the whole world is looking at Iran" and that it was up to Tehran to show that the disputed elections in the country had been fair.
"We are with others, including the whole of the European Union unanimously today, in condemning the use of violence, in condemning media suppression," he said.
"It is for Iran now to show the world that the elections have been fair ... that the repression and the brutality that we have seen in these last few days is not something that is going to be repeated.
"We want Iran to be part of the international community and not to be isolated. But it is for Iran to prove ... that they can respect these basic rights."
Angela Merkel, the German chancellor, who was also attending the summit in the Belgian capital, said Khamenei's speech was "disappointing".
Nicolas Sarkozy, the French president, said that European nations were compelled to speak out "when we see results that are so incoherent".
"A Europe that keeps its mouth shut would not correspond to the values we consider to be European," he said.
"I am always in favour of dialogue with Iran, but when we have to condemn, we condemn."
Britain, Germany and France are all involved in negotiations over Iran's nuclear programme, along with Russia, the United States and China.
Western nations have accused Tehran of seeking to develop nuclear weapons and demanded that it halts all uranium enrichment activities.
Iran denies the charges, saying that its nuclear programme is designed to meet its energy needs.