MPs will Friday vote whether to move the country a step closer to an in-out referendum on its membership of the European Union by 2017.

Hundreds of MPs are expected in parliament for the second reading of a bill brought by a eurosceptic Tory MP.

Prime Minister David Cameron last month ordered all Conservative MPs to give their full backing to the bill, which was rushed out in May by Tory MP James Wharton in a bid to satisfy the increasingly rebellious eurosceptic wing of the party.

Wharton told the BBC he was confident his bill, which had to be tabled as a private members bill instead of a government bill because of Liberal Democrat opposition, would pass its second reading. It is likely to face tougher opposition when it goes to committee and during a third reading because of Lib Dem and Labour opposition.

In January, Cameron vowed to renegotiate Britain's troubled relationship with the European Union and then hold an in-out referendum by the end of 2017, provided that he wins the next general election in 2015.

But disgruntled Conservative eurosceptics want him to enshrine that promise in law before the election to stop any backtracking, as well as to head off the rise of the anti-EU UK Independence Party (UKIP).

The Guardian newspaper reported last week that Labour was contemplating proposing an amendment calling for an in-out vote before 2015.

The bill requires a referendum to be held before December 31, 2017, on the question: "Do you think that the United Kingdom should remain a member of the European Union?"

Private members' bills often fail due to time constraints and Wharton himself warned that any amendments would likely kill the bill.

The issue of Europe has long been toxic for the Conservatives, leading to the downfall of late prime minister Margaret Thatcher in 1990 and weakening her successor John Major.

Cameron came into office in 2010 telling the Conservatives that they were alienating voters by "banging on" about Europe but has since faced three parliamentary rebellions on the issue.

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