Anti-EU campaigners vowed to redouble their efforts yesterday after Ed Miliband rubbished calls for an in-out referendum under a future Labour government.

The Labour leader offered only a vague promise of a referendum in the event of a further "transfer of powers" from Britain to the EU.

But he also argued that it was "unlikely" that there would be any such power transfer during the five-year lifetime of the next Parliament.

Mr Miliband's stance puts Labour in a risky situation in the run-up to May's EU election and next year's general election.

Labour MP John Mann wrote to Mr Miliband urging him to end his hostility to an EU referendum and make Labour a party that "listens to public opinion."

Mr Mann revealed that a survey of 3,000 Labour and undecided voters in his Bassetlaw constituency showed 52 per cent wanting to leave the EU, 17 per cent wanting to stay and 31 per cent undecided.

Labour for a Referendum campaigner Kelvin Hopkins MP warned: "Ed's stance is going to do us no good at all in the upcoming elections.

Mr Hopkins added: "After the European elections, I believe the leadership will have to think again."

Leyton and Wanstead MP John Cryer pledged to step up demands for Labour to hold an EU referendum.

But he denounced Prime Minister David Cameron's promise of a referendum by 2017 as "just a con."

People's Pledge campaigner Stuart Coster announced plans for activists "to make clear to voters which of their candidates for Parliament trusts them to decide on Britain's EU membership."

No2EU spokesman Brian Denny insisted Mr Miliband's pro-EU membership message was essentially the same as the Tories' "electoral con trick."

He said: "His claims that there would be no further transfer of powers to the EU runs completely contrary to EU treaty rules which demand ever closer union.

"It is also ludicrous for him to claim that the completion of a single market in energy and services would cure youth unemployment. For one thing it would outlaw his earlier promises to freeze energy prices."