David Cameron on Monday suffered his largest parliamentary rebellion since becoming prime minister as around 80 Conservative lawmakers defied their leader to vote in favour of holding a referendum on Britain's EU membership. Cameron's government, which is against holding a referendum, in the end won the House of Commons vote 483-111 due to support from the Liberal Democrats -- the Conservatives' euro-friendly junior coalition partners -- and the main opposition Labour Party. But the eurosceptic wing of the Conservative Party delivered Cameron a blow by ignoring whip pressure to vote in favour of a referendum in the biggest show of internal party dissent since he took office in May 2010. George Young, the Conservative leader of the Commons, said he understood that 80 or 81 of the party's 305 MPs had voted against the government, but official figures were not expected until Tuesday. It is also the most serious ever rebellion against a British prime minister on the issue of the EU. After the vote, a spokesman from Cameron's Downing Street office said the government respected the fact that members "felt very strongly" about the issue, but that it had to do with "what is in the national interest." Cameron's strong stance was necessary to preserve the benefits which Britain enjoys from being an EU member but the leader is determined to bring about "fundamental reform" in the 27-nation bloc, added the spokesman in Monday's statement. Labour leader Ed Miliband used microblogging website Twitter to call Monday's result "a humiliation for the PM". Miliband added that it confirmed Tories were "more interested in fighting each other than fighting for Britain." Members who defied the three-line whip -- a parliamentary device aimed at making members obey the party leadership -- are in line to face internal disciplinary action. Although the vote was never to be legally binding, the rebellion is politically significant, particularly as polls suggest it has public support. A YouGov survey for The Sunday Times this weekend found 66 percent of Britons back a referendum on European Union membership. During Monday's pre-vote debate, Cameron told the lower house of parliament he sympathised with those who wanted a new relationship with Brussels, but said the eurozone debt crisis meant now was not the time for a national vote which could see Britain leave the EU altogether. "It's not the right time, at this moment of economic crisis, to launch legislation that includes an in-out referendum," Cameron told the House of Commons at the start of a lengthy debate. "When your neighbour's house is on fire, your first impulse should be to help him put out the flames. ... This is not the time to argue about walking away." The proposed referendum would ask the British public if they want to remain in the EU, leave or renegotiate membership, in the first such vote since 1975. One MP, Adam Holloway, resigned as aide to Europe Minister David Lidington so he could vote for a referendum, saying: "I'm really staggered that loyal people like me have actually been put in this position." Cameron has insisted he is defendng Britain's interests in Europe, and at a stormy EU summit on Sunday he threatened to "exact a price" if the 17 countries that use the euro sought closer integration to deal with the crisis. His stance sparked a row with French President Nicolas Sarkozy, who said he was "sick of you (Cameron) criticising us and telling us what to do" about the eurozone. The Tories were torn apart over the issue of Europe in the 1990s, but even then only 41 MPs defied then-leader John Major in a vote over the Maastricht treaty. George Young played down the comparisons, pointing out to BBC News that the Maastricht vote was over government legislation while Monday's proposal was merely a backbench motion.