³ÉÈË¿ìÊÖ

Tory MPs could be allowed to vote against the Queen's Speech next week as a row over an EU referendum deepens.

Rebel Conservatives have put down an amendment expressing regret that there was no mention of a referendum in the government's plans for the year ahead.

Downing Street said David Cameron was "relaxed" about the move and suggested ministers might be allowed to back the amendment.

Mr Cameron has promised a referendum if the Tories win the next election.

The prime minister has said the pledge to hold a referendum in 2017, once he has negotiated the return of some powers from Brussels, will be in the next Conservative manifesto.

Eurosceptic backbenchers, led by Basildon and Billericay MP John Baron, want legislation in the current Parliament binding the next government to hold a referendum no matter what.

In their amendment, the MPs state that they "respectfully regret that an EU referendum bill was not included" in the Queen's Speech announced on Wednesday.

The amendment has been signed by nearly 30 Tory backbenchers, including former Cabinet minister Cheryl Gillan and former leadership contender David Davis, as well as two Labour MPs.

Downing Street declined to say whether a whip would be imposed on Conservatives if the amendment is selected by Speaker John Bercow for a Commons vote next Tuesday or Wednesday.

Mr Cameron will not vote himself as he will be out of the country on a trip to the US.

Asked if the prime minister feared that the row over EU policy was undermining his authority, his spokesman said: "The PM welcomes the spotlight being put back on his commitment, because he has been absolutely clear that if he is the prime minister post-2015, he will ensure there is a referendum in 2017."

The spokesman said he would not speculate about what may happen "on a vote that hasn't actually been called yet" but stressed Mr Cameron was "happy to look at all ways of strengthening his commitment to an in/out referendum".

Conservative MP Philip Hollobone said he hoped it would be a free vote but a "considerable number" of his colleagues would be prepared to defy the government if it was not.

"There were 81 Conservative MPs who rebelled on the EU referendum issue last time," he told ³ÉÈË¿ìÊÖ Two's Daily Politics programme. "I would not be surprised if the number was in excess of 100 [this time]."

The amendment would stand little chance of being passed as Labour and Liberal Democrat MPs, most of whom oppose a referendum on those terms, as well as many Conservatives, would vote against it.

But Mr Baron has said he wants ministers to remain "focused on this issue".

It comes as the war of words between senior Conservatives over whether Britain should leave the EU continues.

Former Foreign Secretary Sir Malcolm Rifkind described former Chancellor Lord Lawson's decision to back withdrawal as the equivalent of throwing a "hand grenade into a small building".

, Sir Malcolm accused Lord Lawson of wanting to place Britain in the "humiliating" position of being subject to EU rules but having no say in how they are made.

Former Labour Chancellor Alistair Darling, , said it was clearly in Britain's interests to remain in the EU.

Hitting back at Lord Lawson and former Defence Secretary Michael Portillo, who has also come out in favour of leaving the EU, he said inward investment depended on the UK remaining in the "largest trading bloc in the world".

Mr Darling also argued that leaving the EU would diminish Britain's influence in the world and called on "those who believe in this cause to join the fight".