JOIN USA majority of 179 lawmakers voted in favour of reducing diplomatic relations by at least expelling the British ambassador, according to a live broadcast on state radio. Four deputies voted against, and 11 abstained.
Debate continued on whether to stiffen the retaliation further, and lawmakers were discussing whether to also punish other Western countries imposing sanctions.
The final decision will have 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, in coordination with the United States and Canada, announced November 14 new sanctions on Iran over its nuclear programme, after a report by the UN atomic energy watchdog this month suggesting Tehran was researching nuclear weapons.