Iran's parliament voted Sunday to expel Britain's ambassador in retaliation for fresh Western sanctions imposed over Tehran's nuclear programme.
A majority of 179 lawmakers voted in favour of reducing diplomatic relations to the more junior level of charge d'affaires within two weeks and paring economic relations with Britain to a minimum, according to a live broadcast on state radio.
Four deputies voted against, and 11 abstained.
The lawmakers also raised the possibility of punishing "other countries that behave in a manner similar to that of Britain."
"This (bill) is only the beginning," parliamentary speaker Ali Larijani warned.
The bill now has to go to Iran's Guardians Council for approval before it takes effect.
After the parliamentary bill was introduced on Wednesday, Britain said "it would be regrettable" if its ambassador to Tehran, Dominick Chilcott, were to be expelled. Chilcott took up his post last month.
Britain, whose City of London is the world's biggest financial centre alongside New York, said on November 14 it was "ceasing all contact" between its financial system and that of Iran.
That measure, announced in coordination with similar sanctions by the United States and Canada, came a week after report by the UN atomic energy watchdog strongly suggesting Tehran was researching nuclear weapons.
Britain and Canada have embassies in Tehran. The United States does not, having closed it after Islamic students took its diplomats hostage in 1979 following Iran's revolution.
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Iran has dismissed the UN report and insists its nuclear programme is for entirely peaceful purposes.
On Wednesday, Britain said "it would be regrettable" if ambassador Chilcott were to be expelled. Prior to him taking up his post, the British mission was run by a charge d'affaires.
"We believe that it is important to maintain senior channels of communication and especially at times like these. It is only through dialogue that we can solve the problems we face," a spokesman for Britain's Foreign and Commonwealth Office said.
The bill's author, Allaeddin Boroujerdi, who is the head of the parliament's national security and foreign policy commission, said Sunday: "Should Britain cease its hostile approach to Iran, then we can upgrade ties once more."
Several lawmakers, though, had wanted to take the bill further, by cutting off all diplomatic relations to Britain.
"We must sever all ties with Britain," said one, Mahmoud Ahmadi Bighash. "We must place a lock on the British embassy and ignore them until they come begging like the Americans."
Another, Hossein Sobhaninia, said: "Lawmakers should give a crushing response to British threats."
And another, Zohreh Elahian, claimed Britain had an "agenda of sedition aimed at toppling the Islamic republic" following contested 2009 presidential election.
"Britain is one the main (powers) behind anti-Iran resolutions on human rights," she said.
France and other EU nations were expected to unveil more sanctions against Iran at a foreign ministers meeting next Thursday.
Paris has called for a freeze on Iranian central bank assets and an embargo on Iranian oil to be adopted.