TORY backbenchers have moved to maintain the pressure on David Cameron over Europe with a request the UK Government seeks to pass a law before the 2015 General Election.

This would pave the way for an in-out referendum on Britain's membership of the European Union.

Earlier this year in a keynote speech, the Prime Minister pledged there would be a referendum on Britain's membership by November 2017 and that the Conservatives would prepare a draft Bill ahead of the next election. If they won, it would be ready to push through Westminster soon after they took power.

However, John Baron, the Conservative MP for Basildon in Essex, yesterday delivered a letter signed by more than 100 Tory MPs, urging Mr Cameron to go further and write the referendum into law before the next election.

Mr Baron, who has previously moved a Commons Bill to bring about such a law, said the mood among his party colleagues was to continue to press the issue.

He said: "It is a strongly- worded letter, but it is con-gratulatory of the Prime Minister. The referendum promise had to be credible and believable; we got credible because the referendum has an 'out' option.

However, the prospect of Mr Cameron getting a Bill through Westminster before the next election is unlikely to happen, given it will not receive support from the Tories' Liberal Democrat Coalition partners.