Cameron warned of Tory revolt over EU breakaway

Mr Cameron is risking a rift with the left by withdrawing from the EPP, the main coalition of European conservatives that includes Angela Merkel's Christian Democrats in Germany. Right-wing Tories see the EPP as a "federalist" organisation that wants more EU power at the expense of national governments.

Quentin Davies, a former member of the Shadow Cabinet, told Conservative councillors at their conference in Bournemouth yesterday: "A vital struggle is being waged for the soul of the Conservative Party. Human beings define themselves by those with whom they choose to be associated. Does the Conservative Party belong with the great mainstream centre-right parties of continental Europe, or does it belong with populist/nationalist parties in eastern Europe with origins that reach back to the soft fascism that prevailed in countries like Poland and Latvia before the Second World War?

"Are the supposed benefits of leaving the first group for the second worth the price of breaking the signed agreement with the EPP? How can we possibly retain an ounce of political credibility if we become a party which dishonours pledges and tears up signed agreements?"

In 2004, the former Conservative leader Iain Duncan Smith signed a promise that Tory MEPs would be members of the EPP at least until 2009. Mr Cameron promised to end the arrangement when he was seeking right-wing votes in the Conservative leadership contest.