David Cameron acts to stem Tory rebellion over EU referendum At least 50 MPs are said to have signed up to the amendment to the Queen's speech. David Cameron has ordered his ministers to abstain in a pivotal Commons vote on a future EU referendum next week, in a blow to his Eurosceptic colleagues. Tory backbenchers will force a vote on Wednesday condemning the Queen's speech for failing to include legislation committing the country to an in/out referendum. Sources close to the prime minister last week suggested he was "relaxed" about the vote, which is an amendment to the Queen's speech, and could even give all his MPs a free vote. However, over the weekend it emerged that he will not allow Eurosceptic ministers, such as work and pensions secretary Iain Duncan Smith and the environment secretary Owen Paterson, to vote on the amendment, which in effect attacks their own legislative plans. Instead a free vote has only been granted to backbench MPs and parliamentary private secretaries - the senior backbenchers who act as ministerial aides. One senior backbencher said that colleagues were "disappointed" by the move. Despite Cameron's decision, there is growing confidence among Tory MPs that he will ultimately break coalition ranks and deliver the legislation his backbenchers are demanding. They believe that the public will only trust Cameron's promise of a 2017 referendum if there is a law to back it up. By the end of Friday, more than 50 MPs had signed up to the amendment, and sources said that the prime minister had offered no criticism to those behind the move. This could offer political cover. It is a situation not of his making and it gives him the chance to say to the Liberal Democrats that he needs to introduce this legislation. Remember gay marriage wasn't in the coalition agreement either," the source said. John Baron, the Tory MP for Basildon and Billericay, who tabled the amendment, said he had forced the vote because he believed "it is the right thing to do for the country." He said: "The EU is a fundamentally different animal to what we signed up to in 1973 and 1975, and the answer to the eurozone crisis in European capitals is more Europe, more economic and political harmonisation.That is not what we signed up to. People may want that, they might not. But people should have a choice. Baron said that legislation committing politicians to the referendum was crucial to restore trust. We genuinely believe that our commitment on Europe has to be both credible and believable. It's credible because we have an out option in the referendum but it is not yet believable. Legislation would make it more believable than an election manifesto pledge. We underestimate the extent to which the public mistrust politicians when they see them making promises on matters European. And we have to address that public mistrust. Nick de Bois, the Tory MP for North Enfield, who has also signed the amendment, said that an advantage of introducing legislation to potentially guarantee a referendum is that it would flush out the positions of Labour and the Liberal Democrats. "It is about time they made their positions clear in the Commons on whether they will give the British people a referendum or not," he said. The rebellious backbenchers will introduce a private member's bill to introduce legislation enabling the referendum, but they hope a government bill will materialise in due course. Ed Miliband on Saturday reiterated that his party did not believe a referendum should go ahead. At a conference for the Blairite group Progress, he said: "Our national interest lies in staying in the EU and working for the changes that will make it work better for Britain." It is wrong now to commit to an in/out referendum and have four years of uncertainty and a 'closed for business' sign above our country. A senior Liberal Democrat source said Nick Clegg believed that Tory debate over Europe was "a distraction" from the issues that mattered to people, such as economic growth and jobs.