Media playback is unsupported on your device Media caption The BBC's Norman Smith: "I would suggest Mr Cameron is not feeling at all relaxed at the moment"

More than 100 Conservative MPs have defied the government by backing an amendment to the Queen's Speech on an EU referendum.

They "expressed regret" that a bill paving the way for a referendum in 2017, as pledged by David Cameron, was not being brought forward this year.

The move was defeated by 277 votes to 131 as Lib Dems and Labour opposed it.

The backers of the amendment included 116 Tory MPs, representing half of all the party's backbenchers.

Conservative backbenchers were given a free vote - meaning they were allowed to vote whichever way they chose - although ministers were instructed to abstain.

Senior Tories denied the result amounted to a rebellion and said they were united on the issue.

However, Labour said it was a big blow to David Cameron's authority.

Tabled by Conservative MPs Peter Bone and John Baron, the amendment to the government's legislative programme came at the end of a week of Tory wrangling over the issue of the UK's future in Europe and a future in-out referendum on the UK's continued membership of the European Union.

Analysis Conservative MPs who forced Wednesday's vote knew they were unlikely to win the backing of the House of Commons. But they will be buoyed by getting more support than had been expected. They also believe they have helped bring about a strengthening of the Tory commitment to a referendum on Europe after the election. Yesterday the prime minister published a draft bill for an in-out referendum by 2017 and today the chancellor said the Conservative part of the coalition would do everything it could to help any MP who won a parliamentary slot in tomorrow's ballot and took up the cause. Such reassurance appears to have made little difference to tonight's vote. One of the backers of the motion Peter Bone denied it was a rebellion. He said it showed the Conservatives were united behind the need for a referendum on Europe, whilst Labour and the Liberal Democrats were denying the public their say. The prime minister will be hoping fervently that is how it will be seen by the public.

Including tellers, MPs who count the votes, 133 MPs supported the amendment. They included 116 Conservatives - more than half of all Tory MPs who are not part of the government.

Also backing the amendment were 11 Labour MPs, four Democratic Unionists, Lib Dem MP John Hemming and Respect's George Galloway.

BBC News Channel chief political correspondent Norman Smith said the vote showed backbenchers were not happy with the government's approach - which is likely to result in legislation required to pave the way for a referendum delayed until after the next election in 2015.

Speaking after the vote, Mr Bone said the MPs were not defying Mr Cameron but were urging the government to bring forward legislation paving the way for a referendum as soon as possible.

He said Mr Cameron was "doing all the right things" and the Conservative Party was united but their desire to give the British public their say was being "blocked" by Lib Dem leader and deputy prime minister Nick Clegg.

"This is not a rebellion, this is a free vote. In fact, to a certain extent, the prime minister was encouraging us to vote for the amendment because, after all, it's his own policy."

'Deficit of trust'

The prime minister did not take part in Wednesday's vote as he is in the US on a three-day trip.

Mr Baron said he wished Mr Cameron had come out in support of amendment as it would have put pressure on his Lib Dem coalition partners to accelerate the referendum process.

While he trusted the prime minister, Mr Baron said politicians had "broken promises" about EU referendums in the past and the public needed convincing about their intentions.

David Cameron's backbenchers have shown they simply won't give up until he gives in Douglas Alexander, Shadow foreign secretary

"We are not going to walk away," he told the BBC. "We need legislation passed in this Parliament for the next Parliament to bridge that deficit of trust."

In response, Foreign Secretary William Hague said all Conservatives "would like to be able to proceed with legislation in this Parliament...but we are in a coalition".

Media playback is unsupported on your device Media caption John Baron MP: "He [Cameron] should have supported our amendment"

Speaking earlier, Mr Clegg said Tory MPs had "changed the goalposts" over the terms of an EU referendum as the government had already legislated to hold a vote if further powers were handed to Brussels.

Labour have accused the prime minister of "caving in" to his backbenchers and said, while they are not opposed to the principle of a referendum, committing to one now will cause uncertainty and deter investment.

"David Cameron's backbenchers have shown they simply won't give up until he gives in," shadow foreign secretary Douglas Alexander said. "The real risk is that he spends the coming month trying to get his party back in line, instead of focussing on getting our economy back on track."

As an alternative to government-sponsored legislation - which would not be supported by the Lib Dems - the Conservatives published their own draft bill setting out the terms for a referendum by the end of 2017.

The Conservative leadership have said they will support any backbench MP who chooses to adopt the proposal and take it forward as a private members' bill - which would be granted time in the parliamentary calendar for debate.

On Thursday, a ballot will be held to decide which backbench MPs get priority to table private members bills.