The government is unlikely to face a significant rebellion when MPs vote on the EU treaty tonight.
At one stage it was claimed more than 100 Labour MPs were prepared to vote against the government in protest at the refusal to hold a referendum on the EU Lisbon treaty.
The government maintains the Lisbon treaty, agreed by Tony Blair in July, is a reforming treaty and not the same as the abandoned EU constitution, on which ministers promised a public vote.
Labour MP Ian Davidson, who is leading the rebellion, confirmed to the Guardian he does not expect to force a referendum now that the Liberal Democrats have decided to abstain during tonight's vote.
MPs are due to debate the second reading of the EU amendment bill, in which Mr Davidson planned to insert an amendment calling for the bill to be thrown out on the grounds of lack of public consent.
But with the Liberal Democrats now confirmed they will not support the motion, the rebels look certain to be defeated and Mr Davidson confirmed many would now not vote against the government.
Some 18 Labour MPs have signed up to the referendum, along with four nationalists from across the UK.
He told the Guardian: "There are quite a lot of Labour MPs who will take the view that if I'm going to rebel against the government, today is not the day to do it."
Mr Davidson said he was not even holding out for a close vote in tonight's debate, adding: "If I was a government whip, I would want the majority to be well into three figures".
The Conservatives had chosen not to move their own amendment, relying instead on Mr Davidson's.
The Tories have nevertheless been highly critical of Mr Brown's refusal to hold a referendum, although have been less certain in clarifying what they would do with the treaty if it was approved by parliament but not the public.
MPs are preparing for nearly three weeks of debate, in which they will discuss the Lisbon treaty-line-by-line, before it must be approved as a whole.