GEORGE Osborne has called on eurosceptics from other parties to join the Conservatives in supporting a Bill for a referendum on Britain's membership of the European Union as Vince Cable lashed out at the Tories' "endless self-indulgence" on Europe.

The Chancellor's challenge came after James Wharton, a Tory eurosceptic, topped a ballot of MPs, which enables him to put forward his own legislation in a Private Member's Bill.

The MP for Stockton South said he would use the chance to promote the Conservatives' draft Bill on a EU referendum. Tory high command announced it would be subject to a three-line whip, meaning Conservatives will be ordered to vote for it.

However, Private Member's Bills face a struggle to become law and the Conservatives' EU Bill is likely to be opposed and defeated by the Liberal Democrats and Labour because the Tories do not have a Commons majority.

Last night, the LibDem Business Secretary Vince Cable said: "This is just continuing this endless self-indulgent civil war in the Conservative Party about Europe and it is doing the country serious damage because there are potential investors in the UK, who would bring employment here, who are being warned off because of the uncertainty all of this is creating.

"This is not about having a democratic debate. We have already had one. It is about allowing Conservative backbenchers to continue this endless civil war that they have had in their party for 20 years and it is getting in the way of government."

Despite Mr Cable's broadside, Mr Wharton insisted it was time the EU issue was tackled once and for all. He said: "I hope that when it is brought before Parliament, that other MPs from other parties will be able to support it and agree with me that, whatever you think about Europe and our relationship with Europe, the matter needs to be settled and people need to be given a choice."

Later, Mr Osborne said Mr Wharton would have "the full support of the Conservative Party, we are going to make sure Conservative MPs get behind this, we are going to try to persuade rebel MPs from other parties to back us". He added: "When the dust settles, people can see the Conservative Party wants to give the British people a choice – an in/out choice – on Britain's membership of Europe. It's now up to the other parties to say what they are going to do."

Grant Shapps, the Tory chairman, called on Labour MPs to "defy weak Ed Miliband and back our Referendum Bill".

The move follows a show of strength by Tory eurosceptics – 114 of whom on Wednesday voted for a rebel amendment expressing regret the Queen's Speech did not contain a commitment to a referendum on membership of the EU. It was heavily defeated.

Conservative MP John Baron, who was behind the amendment, made clear all his colleagues would now support Mr Wharton's Bill, which is likely to be debated in July.

For Labour, Angela Eagle, said the Tory Party had "descended into chaos on Europe". She claimed the Bill was "spurious" and did not include an implementation clause or money resolution.

In a separate development, senior Tory backbencher David Davis suggested Mr Cameron should force his LibDem partners to give the EU Referendum Bill Government time and, if they refused, he should "call their bluff" on breaking up the Coalition.

Insisting Nick Clegg and his LibDem colleagues were the "tail wagging the dog", Mr Davis urged the PM to get tough.