Former chancellor Kenneth Clarke today launches the Tory European Network, the Conservative campaign for adoption of the single currency.

"Many of the thousands of people who have left the party over the last decade held positive views on Europe and the same is true of most of the four million people who used to vote Conservative but no longer do so," he writes in today's Times newspaper.

He praises Conservative leader and former rival, Iain Duncan Smith, for discussing issues such as the public services and moving away from debate on the euro, but says: "That does not mean that the European issue should not engage Conservatives at all."