Britain's foreign ministry has summoned Iran's ambassador to a meeting after Ayatollah Ali Khamenei, Iran's supreme leader, accused the UK government of being among the "most treacherous" of Western powers.

The ministry contacted Rasul Movaheddian on Friday after Khamenei gave a speech in which he repeated frequent complaints about perceived meddling by Britain and others in Iran's affairs.

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.

'Media suppression'

The foreign ministry said the ambassador would holds talks with Mark Lyall Grant, its political director, later on Friday.

Britain is one of the six nations involved in negotiations over Iran's nuclear programme.

The West accuses Tehran of seeking to develop nuclear weapons, a charge Iran denies.

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.

Brown said: "We are with others, including the whole of the European Union unanimously today, in condemning the use of violence, in condemning media suppression.

"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".