Gordon Brown tonight comfortably fought off attempts to force a referendum on the controversial Lisbon EU Treaty.
The Government won a crucial Commons vote to see off a Tory bid for a plebiscite by 311 to 248, a majority of 63, and its majority only went up after a rebel Labour amendment leaving the door open for a poll on EU membership as a whole.
MPs voted 311 to 247 against rebel Ian Davidson's proposal.
There were initial estimates of 25 rebel Labour MPs and 13 Liberal Democrats.
The MPs' decision left Liberal Democrat leader Nick Clegg facing a series of frontbench resignations from rebels who had defied his orders to abstain on the key votes.
Environment spokesman Tim Farron, Scotland and Northern Ireland spokesman Alistair Carmichael and justice spokesman David Heath announced they would quit.
Mr Carmichael said: "For a frontbench spokesman to defy his party's whip is a serious situation and one which I have not taken lightly.
"It is not something which can be done while remaining in post and I have therefore offered my resignation to Nick Clegg as the party's shadow secretary of state for Scotland and Northern Ireland.
Mr Clegg, who emerged as the big loser from tonight's Westminster drama, said: "I greatly regret the loss of David, Tim and Alistair from the shadow cabinet. They have served with great distinction and commitment.
"However, as they have recognised, the shadow cabinet cannot operate effectively unless the principle of collective responsibility is maintained."
Earlier, Mr Brown dismissed calls for a referendum on the controversial change to EU structures, insisting it was not needed.
Clashing with Conservative leader David Cameron in the Commons, Mr Brown said: "If this was a constitutional treaty, we would hold a referendum. But the constitutional concept was abandoned."
Foreign Secretary David Miliband insisted that a referendum should only be held when a "fundamental" shift of power was to take place.
But Mr Miliband said the Treaty of Lisbon did not represent a fundamental shift and any referendum was, in a sense, an abdication of power by Parliament and the Government of the day.
He said: "This Government intend to make no such abdication of their responsibilities, neither do we intend to invite the House to abdicate from its responsibility."
Shadow foreign secretary William Hague told MPs: "What has really changed between Tony Blair standing at the despatch box and saying let battle be joined in a referendum in April 2004 and the current Prime Minister saying let battle be avoided at any cost and please don't let me be photographed at the signing ceremony?
"Two things have changed - the General Election of 2005 was got out of the way and the Government have decided that a referendum cannot be held because they do not think they would win it."
Leader of the Labour rebels Mr Davidson told MPs: "If we want to stop the disillusionment and cynicism about politics, we've got to recognise 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 that we are honour-bound to abide by our commitment to a referendum."
But all the rebel arguments came to nothing as MPs voted to approve the controversial treaty - which has yet to go forward to win approval in the House of Lords, where fresh opposition is certain to come.Reuse content