British PM Cameron pressed to put EU membership to a vote British Prime Minister David Cameron will publish a draft bill on Tuesday to prepare for a referendum on Britain's European Union membership - a political gamble aimed at placating anti-EU lawmakers who are pressing him to take a harder line on Europe. The Conservative leader's concession comes less than four months after he pledged to renegotiate the terms of Britain's EU membership and then hold a vote before the end of 2017. Mr. Cameron's referendum promise in January failed to satisfy Conservative critics who now want him to hold the vote before the next national election in 2015 or pass a law committing the party to the vote. "The Conservative Party will [on Tuesday] publish a draft bill to legislate for an in-out referendum by the end of 2017," a senior Conservative source told reporters in Washington after Mr. Cameron met with U.S. President Barack Obama. "We will examine all opportunities to bring the bill before Parliament, including a private member's bill," the source said. It will be hard for the Conservatives to push a referendum bill through Parliament because it will likely be opposed by their pro-EU coalition partners, the Liberal Democrats, as well as the opposition Labour Party. As many as 100 Eurosceptic Conservative members of Parliament are expected to back an amendment this week criticizing legislative plans unveiled by the government because they did not include a bill paving the way for a referendum on EU membership. Conservative lawmaker John Baron, one of the two figures behind the amendment, said Mr. Cameron's promise of a draft bill would not persuade him to back down. I am sticking by what I am saying. They know that this option could very well fail," he told Reuters. A far better approach would be to have the courage to support our amendment on Wednesday. Mr. Cameron came to power in a coalition government three years ago after telling his party in 2006 to "stop banging on about Europe," an issue that has divided the Conservatives for decades and helped bring down two of his predecessors, Margaret Thatcher and John Major. Conservatives have been rattled by the growing popularity of the UK Independence Party, which campaigns for Britain's withdrawal from the EU and tighter immigration laws. UKIP's poll rating has climbed steadily since Mr. Cameron's EU referendum pledge, with the party taking a quarter of the vote in local elections this month. The Labour Party said Mr. Cameron had "lost control of the agenda and lost control of his party" when he should be working on reviving Britain's economy. "This seems to be just the latest panicked response from the Prime Minister, who is now following, rather than leading, his backbenchers," Labour foreign affairs spokesman Douglas Alexander said in a statement.