By Guy Faulconbridge and Mohammed Abbas
BIRMINGHAM (Reuters) - A referendum on Britain's ties with the European Union would be the best way of agreeing a fresh settlement with the 27-member bloc, Prime Minister David Cameron said on Tuesday, as pressure mounts within his party for a vote.
The Conservative Party's restive "eurosceptic" right wing is clamoring to claw back powers from Brussels. Some want a simple vote on staying in the EU or leaving, fearing that the party could lose votes to the anti-Europe UK Independence Party at the 2015 election.
Cameron says Britain should remain in the EU, Britain's biggest trading partner, but renegotiate terms as the 17 members of the EU's currency union redefine their own ties to tackle their sovereign debt crisis.
Speaking to the BBC, Cameron gave no time frame for a vote or any indication of what could be asked at a referendum. The prime minister has said he is against an "in/out" plebiscite.
"When we achieve that fresh settlement, it needs consent, either at a referendum or a general election," Cameron said on the sidelines of the Conservative Party conference in the English city of Birmingham.
"Frankly, a referendum is obviously the cleanest, neatest and most sensible way of doing that."
Europe has divided the centre-right Conservatives for decades and helped to bring down the party's last two prime ministers, Margaret Thatcher and John Major.
Cameron has promised a referendum after 2015 on any future EU treaty, and has pledged to avoid getting entangled in costly solutions to the euro zone debt crisis and to try to repatriate some powers from Brussels.
But some Conservatives want Britain to renegotiate its relationship with Europe now, disappointed by Cameron's U-turn on a pre-election pledge for a vote on the Lisbon Treaty.
"Europe is changing - the euro zone is going to integrate .... it is necessary if they are going to save the single currency, but I think that does open up the opportunity for Britain to get a fresh and a better settlement with Europe," Cameron said.
"I am committed to making sure we do everything to set that out in the run-up to the next election, to get that fresh settlement and then seek fresh consent for that settlement."
On Sunday, Cameron threatened to scupper EU budget talks unless other members of the bloc agreed to "proper control" of spending, without specifying what arrangement Britain would accept.
He also lent his support to a proposal for two EU budgets - one for the euro zone and another for cash-strapped Britain and the other nations outside the single currency.
The prime minister used Britain's veto in December to block an EU-wide pact designed to help the euro zone, a move that delighted eurosceptics in his party but dismayed his Liberal Democrat coalition partners and other European leaders.
A deal was eventually agreed without Britain.
(Reporting by Mohammed Abbas and Guy Faulconbridge; Editing by Kevin Liffey)