LONDON - Prime Minister David Cameron ratcheted up the rhetoric against Europe on Sunday by demanding a radical change to Britain's ties with the European Union and offering the prospect of an exit from the continent's principal treaty on human rights.
Europe poses one of the biggest obstacles to Cameron's re-election in 2015 and he is under pressure from Conservative lawmakers to stem the loss of support to the UK Independence Party (UKIP), which calls for an immediate withdrawal from the EU.
Cameron said the EU will have to renegotiate the treaties on which it was founded, an idea rejected by some EU members as being too complicated and time-consuming.
"My goal is to renegotiate our relationship with Europe, very radically," Cameron told the BBC at the start of his Conservative Party's conference in Manchester, northern England."We need a treaty renegotiation, I am convinced one has to happen."
Cameron said in January that he would negotiate Britain's EU relationship before holding an in/out referendum by the end of 2017, provided he wins the next election in 2015.
That promise was seen as an attempt to mollify anti-EU Conservatives and mount a stronger challenge to UKIP.
Some EU members have warned Britain that they will resist attempts to reclaim powers unilaterally. Business leaders say talk of Britain leaving its biggest trading partner could undermine confidence and investment.
German Chancellor Angela Merkel, who was re-elected with a strong mandate this month, has started talking about powers flowing back to member states from Brussels, but "she means something different from the British" and is still committed to a more integrated EU, an aide told Reuters.