LONDON (Reuters) - Most grassroots members of David Cameron's Conservatives want the prime minister to offer Britain a referendum on its membership of the European Union after the next parliamentary election, according to a survey.
A poll for Channel 4 News conducted by right-leaning website ConservativeHome showed more than four out of five Conservative Party members want a vote either in the next parliament or after a renegotiation of Britain's terms of EU membership.
Cameron pulled the plug on his promise of a referendum on Europe's Lisbon Treaty before the 2010 election, replacing it with a pledge to hold a plebiscite on any future treaty or transfer of powers to Brussels.
Last year, he angered European leaders, but went some way to appeasing the unruly anti-EU wing of his own party, by opting out of an EU-wide economic pact, designed to help solve the euro zone debt crisis.
Cameron has said he wants Britain to remain an active player in the European Union but some of his party believe he has had his hands tied by failing to win an outright majority in 2010 and forming a coalition partnership with the europhile Liberal Democrats.
Seventy percent of the 1,604 Conservative party members polled by ConservativeHome said they would vote in favour of pulling out of the EU if there was an immediate referendum.
Party infighting over Britain's relationship with Europe caused considerable problems for former Conservative prime ministers Margaret Thatcher and John Major, although today's "eurosceptics" lack a credible and prominent ringleader.
There has been some speculation that the Conservative leadership could offer a referendum in its next election manifesto, as the whole European Union comes under strain with Greece potentially facing an exit from the euro.
Successive Conservative and Labour prime ministers have fought to limit the power Brussels has over British laws and regulation, specifically where Britain's prized financial services sector is concerned.
The opposition Labour party - Cameron's main rivals in the next parliamentary elections due in 2015 - is also toying with offering voters a choice on Britain's EU membership.
Conservatives have been worried to see the UK Independence Party - which wants Britain to leave the EU - progress in local government elections. Cameron could see his vote split by UKIP in 2015, potentially derailing his attempts to win an outright parliamentary majority.
Reporting by Matt Falloon; Editing by Andrew Heavens