UP to 100 Conservative MPs will defy David Cameron today (Wednesday, May 15) by demanding a quickfire Bill to guarantee a referendum on quitting the European Union.

The prime minister insisted he was “profoundly relaxed” about the move – despite his previous vow to stop his party alienating voters by “banging on about Europe”.

And he rushed out a draft Bill of his own to try to calm dissent, despite Liberal Democrat opposition blocking any chance of it becoming law in this Parliament.

But one former Conservative minister, Nicholas Soames, branded the rebel MPs “irresponsible”, saying: “The public will think we look like we don't know what we are doing.”

And Sir Ming Campbell, the former Lib Dem leader, said the Tory turmoil had echoes of the way rows over Europe destroyed John Major’s premierships.

Last night, Stockton South MP James Wharton said he would back the amendment to last week’s Queen’s Speech, that expresses “regret that an EU referendum Bill was not included”.

And, asked if he would vote to quit the EU if there was a referendum today, he replied: “With the EU has it is now, I would have to vote to leave – but there won’t be one.”

Mr Wharton said: “This amendment will send a clear signal that the Conservative party wants to give people a say on our relationship with the European Union.

“I accept that is difficult to deliver at this time – because of the unanimous opposition of the Liberal Democrats – but this is a helpful opportunity to make our position very clear.”

The MP insisted the Tories were not being damaged by the fresh Euro-rows, adding: “That will only happen if it distracts from other things we are doing.”

Late on Monday, Mr Cameron rushed out a pledge to publish his own draft Bill, to persuade his MPs to back down – a strategy that appeared to have failed comprehensively.

When it appeared, it promised a referendum by the end of 2017, with the question: “Do you think that the United Kingdom should remain a member of the European Union?”

However, because it can only be taken forward by a backbencher, it has virtually no chance of becoming law - because of a lack of Parliamentary time.

Some critics said that – at just 490 words, compared with the 62,683 words in the Scottish Independence Referendum Bill – it bore all the hallmarks of panic.

But, speaking the US, and asked if he had panicked, Mr Cameron replied: “Not at all. If this was a Conservative-only government, we would just get on and legislate.

“We can't do that, because we are in Coalition. But I have always said that anything we can do to strengthen, add credibility to the pledge … we should do.”

Up to 15 Labour MPs are also expected to back the amendment today – despite Ed Miliband arguing it is the wrong time to commit to an EU referendum.