Labour rebels were tonight defeated in their attempt to force the government to "keep a promise" to hold a referendum on the Lisbon treaty. ( Guardian )
But in an unexpected turn of events, a separate Tory amendment received virtually the same level of support as the Labour call for a referendum.
While the Labour amendment was defeated by a majority of 64 (311 against, 247 for), the Tory amendment was defeated by 63 votes (311 to 248).
To the embarrassment of Gordon Brown, the result suggests a number of Labour rebels backed the Tory bid to have a referendum, as well the one tabled by Ian Davidson, Labour MP for Glasgow South West.
While the Tory proposal favoured a straightforward referendum, Davidson's amendment set out measures to put in place a referendum on the Lisbon treaty and also allow the possibility of another referendum on Britain's membership of the European Union.
The results put to rest an issue which has caused bitter divisions within both the Labour and the Liberal Democrats.
MPs in both parties are uncomfortable with their leader's insistence that respective manifesto commitments to hold a referendum were null and void because the promise had been made on the basis of the constitution, not the EU treaty which replaced it after the constitution was abandoned.
About two dozen Labour MPs and 10 Liberal Democrats had been expected to defy their respective leaderships and vote in favour of a referendum, amid a series of polls which suggest widespread public support.
Speaking in the debate earlier today, Davidson told MPs they were "honour bound" to hold a referendum.
He said: "If we want to stop the disillusionment and cynicism about politics, we've got to recognizes that the people out there expect us to keep our promises when we make them and that's why, on this side of the House, I believe we are honour bound to abide by our commitment to a referendum."
But foreign secretary David Miliband said there were "big differences". The structure of the constitution abandoned all previous treaties that governed the EU, but the Lisbon Treaty did not,"he said.
"Secondly, in respect of a range of policies, notably on justice and home affairs, the content is different.
"Thirdly, in respect of the consequences, the constitutional treaty was alleged by many Tory MPs to be a slipway to a superstate.
"Under the Lisbon Treaty there is an agreement there shall be no further institutional reform for the foreseeable future.
"So in structure, and in content, and in consequence this is different."
In his first real test of leadership, Nick Clegg saw a number of Lib Dems defy a three line party whip to abstain on the amendments.
Three of his front bench are already believed to have quit their post to vote with the Tories for a referendum.
David Heath, the justice spokesman, Tim Farron, the countryside spokesman, and Alistair Carmichael, the Scotland and Northern Ireland spokesman, were among the most senior MPs to indicate they would rebel.
The referendum led to heated exchanges between the three party leaders at prime minister's question time earlier today.
Tory leader David Cameron, the Conservative leader, accused Brown of not supporting a referendum because he was worried he would lose it.
Pointing out that all three main political parties promised a referendum on the proposed EU constitution in their 2005 election manifestos, Cameron said: "A referendum was promised, it should be delivered. If Labour can't trust the people, why should the people trust Labour?"
But Brown insisted that the Lisbon treaty was different from the constitution. "If you want to persist in talking about the 'United States of Europe' and a constitutional treaty, you have no support in the rest of Europe," he told Cameron.
"If your party had really changed and moved to the centre, you would be standing up to your backbenchers - you would be leading them instead of following them.
"You would be standing up to the Eurosceptics instead of appeasing them. You would be moving to the centre of Europe instead of being left at the margins of Europe."
Liberal Democrat leader Nick Clegg said Mr Brown had "bottled" a referendum and said voters would not believe in the European Union until politicians were prepared to stand up for it.