LONDON (Reuters) - Nearly half of Britons would vote in a referendum to leave the European Union and less than a third to stay in, according to a poll highlighting divisions facing Prime Minister David Cameron.
Polling company YouGov said on Thursday 49 percent favored leaving the EU, 28 percent would vote to stay in the 27-nation bloc, 17 percent were undecided and the rest would not vote.
The British leader is under growing pressure from rebels within his party to take a tougher stance with Brussels when he attends EU budget talks later this month.
He also faces an increasing challenge from the anti-EU UK Independence Party and hardening attitudes against Brussels at a time of austerity and worries over the euro zone debt crisis.
The YouGov results - based on interviews with 1,637 adults in late October - are in line with other surveys and have been broadly steady this year. A related poll of 1,000 Germans found 57 percent wanted to stay in the EU and 25 percent to leave.
Cameron held EU talks in London on Wednesday with German Chancellor Angela Merkel, who warned Britain not to turn its back on Europe.
"Cameron must attempt to be perceived as a constructive member of the Union, while at the same time trying to satisfy public opinion in his own country," said Joe Twyman, YouGov's director of political and social research.
Britain's often lukewarm approach to Europe has angered many in the bloc and fuelled talk of London slipping out of a club it joined in 1973. Britain held a referendum in 1975 on membership of the EU's forerunner, with 67.2 percent of voters in favor and 32.8 percent against.
Cameron has urged his party to stop "banging on" about Europe, an issue that has divided them for decades.
He opposes holding a referendum on Britain leaving or staying in the EU. Instead, he wants to renegotiate its role in Europe and seek voters' consent for the changes, either at a referendum or a general election.
The next test of Britain's often-fraught relations with Europe comes at talks this month in Brussels to secure agreement on the long-term EU budget. Cameron has threatened to veto a deal if he feels it is not in Britain's interests.
Reporting by Peter Griffiths; editing by Andrew Roche