LONDON (Reuters) - Support among Britons for staying in the European Union is at its highest in 23 years, according to a poll on Wednesday, even though the anti-EU UK Independence Party (UKIP) is gaining popularity.
Under pressure from UKIP and Eurosceptic members of his Conservative party, British Prime Minister David Cameron has pledged to hold a referendum in 2017 on Britain's EU membership if his Conservative party wins an election next year.
But the poll by Ipsos MORI showed just over half of Conservative supporters favoured staying in the EU, indicating Cameron has a fine line to tread and could risk losing support by taking too hardline an approach to Europe.
Among the other parties, 73 percent of supporters of the opposition Labour party and 82 percent of backers of the Liberal Democrats, the government's junior coalition partner, favour EU membership.
By contrast, just 11 percent of supporters of UKIP, which earlier this month won its first elected seat in parliament, said they would vote to stay in.
Overall, 56 percent of Britons would back staying in the EU, compared with 36 percent who would choose to leave. That was the highest level of support for Britain's EU membership since 1991, and showed a switch from 2012 when more people said they wanted to exit the bloc than remain in.
"Support for Britain's membership is up significantly since the depths of the eurozone debt crisis in 2011, although that does not mean that the public simply want the relationship to stay the same," said Gideon Skinner, Ipos MORI's head of political research.
Cameron, who has seen UKIP's opinion poll support rise to double figures and two of his lawmakers defect to the anti-EU party, has promised to renegotiate Britain's ties with the 28-nation bloc, before the proposed 2017 referendum.
One in three of those surveyed by Ipsos MORI said they would like Britain to be part of an economic community in Europe without political links. Only 14 percent said they would like to see closer integration with EU member states.
Cameron has long said he would like Britain to stay in a reformed EU, but British Foreign Secretary Philip Hammond said last week the bloc would have to come up with a meaty reform deal if it wanted to avoid Britain leaving.
(Reporting by Kylie MacLellan; Editing by Larry King)