Clarke sets leadership fight alight as he seeks top prize for third time

Today the 65-year-old former Chancellor will mount a blistering attack on Tony Blair's actions in Iraq as he makes the first in a series of speeches. He will condemn the Prime Minister for failing to ensure there was a proper plan for post-war Iraq and may make a link between the conflict and the London bombings in July.

Mr Clarke, who defied the Tory leadership by opposing the war, said he "always foresaw we would be in difficulty" in Iraq. He said the task now was to extricate Britain from the "dreadful mess" with some honour and address relations with the Muslim world.

He will go head to head with David Cameron, the 38-year-old shadow Education Secretary, as they struggle to emerge as the main challenger to the front-runner David Davis, the shadow Education Secretary.

Mr Cameron will also make a speech today on " modern compassionate Conservatism" and "quality of life" issues. Rejecting a Thatcherite approach to social issues, he will say: "We understand that there's a 'we' in politics as well as a 'me', that there is such a thing as society, it's just not the same thing as the state."

As allies of Mr Cameron described his heavyweight rival as "too old", Mr Clarke dismissed the idea as "faintly absurd". He told the BBC: "I have not noticed I have got any older. Personally, I feel as fit as I ever did. I am enjoying my politics at least as much as I ever did. Ann Widdecombe, the former Home Office minister, who is backing Mr Clarke, said his age should not count against him. She said: "We went for a young and very bright and capable person in 1997 [William Hague], no progress. We went for youth again in 2001 [Iain Duncan Smith], no progress. When we finally then handed the party over to somebody in their sixties, in the shape of Michael Howard, we made the first real electoral gains that we have made for more than a decade."

Ms Widdecombe suggested that Mr Cameron was too inexperienced, saying he was "very able and very clever" but this was not the time for him to lead the party. "Either we are serious about being in government, or we are not, and if we are, we must go for Ken Clarke," she said.

Mr Clarke also told the BBC the Tories must be seen as a "credible alternative government in-waiting that is ready to go, looks as though it could handle competently and effectively the big issues as they come along. I just happen to think that I now fit the bill to do that."

Andrew Mitchell, the shadow International Development Secretary and a close ally of Mr Davis, predicted a two-man race between him and Mr Clarke. He said: "Ken is one of the very big beasts in the party. I supported Ken last time, he is a good friend of mine. But I think that his time has gone, and that the right man to lead the Tory party now, in the dire position that we are in as a party, is David Davis."

Sir Malcolm Rifkind, the shadow Work and Pensions Secretary, said his campaign would not be knocked off course by Mr Clarke. He announced a four-strong election team, including two MPs who backed Mr Clarke in 2001- Jacqui Lait and Peter Bottomley.