Britain's opposition Conservatives chose David Cameron as their new leader yesterday, opting for youth to revive their fortunes and challenge Prime Minister Tony Blair after three successive election defeats.

The centre-right party, which dominated 20th century British politics under leaders such as Winston Churchill and Margaret Thatcher, has struggled to drag itself out of the wilderness and Mr Cameron, 39, is the fifth Conservative leader in eight years.

But there is new hope in the party as the popularity of ruling Labour wanes. Mr Blair has said he will not fight a fourth election and a faltering economy is clouding the future of his likely successor Finance Minister Gordon Brown.

Supporters believe that even though Mr Cameron comes from a privileged background he can widen the party's appeal to voters in the centre ground in the same way Mr Blair revamped Labour to win a landslide in 1997 after 18 years in opposition. "I want us to give to this country a modern, compassionate conservatism that is right for our times," Mr Cameron told a euphoric party gathering after the result was announced.

"Now that I have won, we will change," he said.

Mr Cameron overwhelmingly beat David Davis, the party's experienced home affairs spokesman and a right-winger, winning 68 per cent of nearly 200,000 votes cast by party members.

His aides said the scale of the result would give him the authority to stamp his "modernising" blueprint on the party. With Mr Blair's days numbered, the Conservatives are focusing their fire on Mr Brown who they see as vulnerable because he is seen to be more aligned with traditional left-wing policies.

"This man is the road block to reform. He is the person who is holding Britain back," Mr Cameron said of Mr Brown.