David Cameron is facing a new Conservative rebellion over Europe as his MPs challenge his authority by renewing their demands for a referendum.

Tory Eurosceptics took the unusual step of tabling an amendment to the Queen’s Speech regretting the absence of a Bill to guarantee Mr Cameron’s promise to hold an in/out referendum by 2017. It could be put to a Commons vote next week.

John Baron, the Tory MP who tabled the amendment, said: “The objective is to keep the Government focused on this issue. It would send a clear message that we are not going away and that there is a large body of opinion inside and outside this place that believes that legislation is right for a EU referendum.”

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Downing Street insisted that Mr Cameron is “relaxed” about the amendment. But the Liberal Democrats will oppose it.

The Prime Minister today criticised both Eurosceptics and Europhiles. He told a London conference on global investment: “I am faced…. by two groups of pessimists. There are some pro-European pessimists who say, 'you have to, in Europe, simply sign-up to every single thing that anyone in the EU suggests. You sign every treaty, you sign everything - there is no alternative'. I think they are completely wrong.

"The second group of pessimists say there is no prospect of reforming the EU, you simply have to leave. I think they are wrong too. I think it is possible to change and reform this organisation and change and reform Britain's relationship with it."

Lord Lamont, the former Chancellor, became the latest senior Tory to support Lord Lawson’s call for Britain to withdraw from the EU but said: “It is perfectly logical, and reasonable actually, to make one final attempt to renegotiate our relationship.”