Britain's Conservative Party leader David Cameron speaks during a press conference in central London, on November 4, 2009. British opposition leader David Cameron, tipped to be the country's next prime minister, outlined a new policy on Europe Wednesday after dropping a pledge to hold a referendum on the Lisbon Treaty. Cameron's Conservative Party U-turned on a 'cast-iron guarantee' to hold a national vote on the European Union's reform treaty after the Czech Republic gave it the green light Tuesday. It will now come into force on December 1.