A potentially divisive House of Commons vote on Britain's future in Europe looks set to go ahead on Wednesday, despite David Cameron's dramatic decision to publish draft legislation to pave the way for an in/out referendum in 2017.

One Conservative eurosceptic branded the announcement, just hours after Mr Cameron's White House meeting with US President Barack Obama, "undignified" and said it was a sign of "chaos" in 10 Downing Street.

Another said the draft Bill was a "second-best" option and urged the PM to give his backing to a Yes vote on an amendment to the Queen's Speech attacking the lack of referendum legislation in the Government's legislative programme for the coming year.

Labour said the Prime Minister's "weakness" had made Europe a "leadership issue" for Mr Cameron, whose latest initiative was about "trying to get his party back in line rather than getting the economy back on track".

Downing Street said the amendment - signed by at least 78 MPs, including 67 Tories - was "clearly in line with Conservative Party policy", but said ministers were being told not to vote for it because it conflicts with the Government position agreed with Liberal Democrat coalition partners. Backbenchers and ministerial aides are being given a free vote.

Mr Cameron is unable to put Tuesday's Bill forward as Government legislation because of opposition from Lib Dems, who have said they are "nonplussed" by his gambit. Conservatives will instead publish the draft Bill in the hope that it will be tabled by a backbench MP as a Private Member's Bill following Thursday's ballot.

Tory MP Douglas Carswell said the draft Bill was "what I wanted" and urged fellow-eurosceptics now to put their efforts into ensuring a Private Member's Bill is tabled and passed. But other Conservatives said they would push ahead with Wednesday's vote, which looks set to divide the coalition.

Basildon and Billericay MP John Baron described the draft Bill as "a small step in the right direction", but added: "No 10 knows that a Private Member's Bill could fail. A far better approach is for the PM to have the courage to support our amendment on Wednesday, which would force Labour and the Liberals to decide. If we won, he would then have the mandate to introduce legislation through the normal channels if he chose to do so."

And Kettering's Philip Hollobone predicted that about 100 Tories would back the amendment. Asked about the way the draft Bill was announced during Mr Cameron's visit to the US, Mr Hollobone told BBC Radio 4's World At One: "It is undignified and there is some chaos in Number 10 this week."

A Downing Street spokesman denied that the Government was in chaos over the Europe issue and said Mr Cameron was "very happy" for tomorrow's vote to go ahead, as it would put a spotlight on his referendum pledge.