The rebellion by almost half of the Conservative Party backbench MPs over a motion for a referendum on the conditions of Britain’s membership of the European Union is the largest ever faced by a Tory leader.

The motion called for a referendum as to whether Britain should remain in the EU on current terms, renegotiate those terms, or leave.

Prime Minister David Cameron had taken the strongest possible measures to limit a rebellion by the sizeable Eurosceptic contingent in his party. He imposed a three-line whip—the strictest order to back the government’s line—and rescheduled the vote for Monday evening so that he could participate in the debate.

In the end, a total of 81 Tory MPs defied the government and a further 12 abstained. This is almost double the number that defied Prime Minister John Major in 1993 in the vote on the Maastricht Treaty that led to the creation of the EU and, eventually, the euro currency. Two Tory parliamentary private secretaries—Stewart Jackson and David Lidington—lost their positions for opposing the government.

The rebellion involves more MPs than the size of the parliamentary majority held by the coalition between the Tories and Liberal Democrats. The government won the vote comfortably—by 483 votes to 111—only because Labour and the Lib-Dems joined Cameron in instructing their MPs to oppose the motion. Just 19 Labour MPs and one Liberal Democrat disobeyed.

Cameron and much of his cabinet have in the past been among the most vocal critics of the EU. In an interview ahead of the vote, Foreign Secretary William Hague, a leading Eurosceptic, stressed that he had “argued for more referendums than almost anybody else. I've argued against the euro more comprehensively than almost anybody else.”

He angered Tory backbenchers, however, when he described the motion as parliamentary “graffiti.” Hague did not participate in the vote, citing a government trip to Australia.

If Hague, Cameron and others appear to have retreated from their former positions, it is because Britain’s banks have a powerful vested interest in ensuring that the EU agrees to hand over further substantial tranches of public funds to Europe’s financial institutions. While they are less directly exposed to Greek debt than France and Germany, British banks are heavily involved in insuring the holdings in Greek bonds of global investors.

In the debate Monday evening, Cameron said he sympathised with backbench sentiment and was “firmly committed to… bringing back more powers from Brussels.”

But he warned that the crisis in the euro zone meant the time was not right for a referendum. “It's not the right time, at this moment of economic crisis, to launch legislation that includes an in-out referendum,” he said.

“When your neighbour’s house is on fire, your first impulse should be to help him put out the flames, not least to stop the flames reaching your own house. This is not the time to argue about walking away. Not just for their sakes, but for ours.”

Cameron was speaking ahead of today’s EU summit to agree a “rescue package” for Greece. This is said to include plans to expand a bailout fund for the euro zone by €1 trillion. The fund is aimed at protecting European banks from impending bankruptcy by Greece. In the meantime, European leaders have stepped up demands for even harsher austerity measures in Greece and other countries to fund the bank bailout.

But such plans are themselves the focus for the explosive national antagonisms that sustained the Tory back-bench revolt.

At a meeting of EU leaders Sunday, Cameron was reportedly subject to a “tirade” by France’s Nicolas Sarkozy because of his pressing for non-euro zone members to sit in on discussions at today’s summit. “You have lost a good opportunity to shut up,” Sarkozy was quoted as telling the prime minister. “We are sick of you criticising us and telling us what to do. You say you hate the euro and now you want to interfere in our meetings.”

Cameron’s supporters claimed that Britain’s participation in the summit was proof of the correctness of the government’s line.

In parliament, Cameron stressed that the crisis in Europe should be used as an opportunity to reshape the EU more in Britain’s interests. His government would use its veto power to protect the City of London against proposed EU treaty changes aimed at strengthening fiscal coordination in the euro zone, he indicated. And he praised demands by European Commission President José Manuel Barroso for greater labour “flexibility” so that the EU could compete against the United States and its major rivals.

“These are arguments which Margaret Thatcher made to drive through the single market in the first place, and which every prime minister since has tried to push. I am no exception.”

This failed to reassure backbench MPs, who believe that the euro zone, as it is presently constituted, is essentially finished. The outcome, they believe, will be a more politically and fiscally integrated version of the EU under German domination that will inevitably conflict with the City of London and its interests.

David Davis, who challenged Cameron for party leadership in 2005, said, “We have been told this is the wrong time. This is the time when all the claims of Nicolas Sarkozy and Angela Merkel are to centralise the EU even more to create a fiscal union. It will have an impact on Britain, as the prime minister has said. So this is absolutely the time to think about this. We should be protecting ourselves from the consequences of the euro zone.”

These rising national tensions are fuelling divisions within the entire political establishment, and the Conservative Party in particular.

Commentators said the vote was as much directed against Cameron as the EU. The prime minister was criticized for responding in a heavy-handed manner to a parliamentary vote that committed the government to nothing.

There is bitterness amongst Tory ranks that Cameron decided on a coalition with the Liberal Democrats after failing to win an outright majority in the 2010 general election. While the Liberals were paid off for their support with a referendum on establishing an alternative vote electoral system—which they lost—the prime minister has set his face against support for a referendum on Europe, despite having previously used the issue as a stick to beat the Labour government.

Virtually every Tory that spoke in the five-hour parliamentary debate opposed Cameron. According to the ConservativeHome web site, nearly two-thirds of Tory members do not believe Cameron is serious about renegotiating Britain’s relations with the EU. Several of the Tory MPs who rebelled were elected only in 2010, something that is considered significant for Cameron’s leadership.

The United Kingdom Independence Party (UKIP) held a rally outside parliament while the vote was taking place. Although UKIP has only two MPs, much of its leading personnel are former Tories and it has broad support among the Conservative rank-and-file.

Writing in the Telegraph, Benedict Brogan opined, “The party is now divided. Not about Europe: there is far more agreement now than there was 20 years ago. No, the division is over Mr. Cameron. The outcome of the vote, if it’s as bad as suggested, tells us Mr. Cameron does not command the loyalty of a sizeable chunk of his colleagues. This is ominous.”