KENNETH Clarke last night squared up to Sir Malcolm Rifkind as the Conservative heavyweights became the first to officially enter the battle for the party leadership.

KENNETH Clarke last night squared up to Sir Malcolm Rifkind as the Conservative heavyweights became the first to officially enter the battle for the party leadership.

Just hours after former Chancellor Mr Clarke said he was desperate to lead the Conservatives back into power, one time Foreign Secretary Sir Malcolm confirmed he would also run - setting up a fight for the One Nation vote, the party's liberal wing.

Bookmakers' favourite David Davis is expected to announce his candidacy when the contest officially opens and David Cameron's camp says he is also "almost certain" to run.

Mr Cameron, who earlier had rejected calls to form a dream ticket with Mr Clarke, will bury the prospect today by interrupting a family holiday in Devon to deliver a speech clashing with one by Mr Clarke.

Mr Clarke yesterday met supporters to discuss his campaign. He unveiled new backers in MPs Anthony Steen and Bob Walter after his bid had been endorsed earlier by Suffolk South MP Tim Yeo.

Mr Clarke said he was determined to see the Conservatives back in power and said he said he was the man to lead them there.

"I am getting frustrated by the fact that we have been out of office for eight years. I think the standards of politics are declining, the standard of government is getting very bad, some serious errors have been made by this Government.

"I desperately want to see the Conservative Party make quicker progress getting back into power. I've thought about it and I think I can actually lead the party and do that because I want to see the party do that, I want to see them win again."

Mr Clarke's announcement put pressure on Sir Malcolm to renounce his ambitions. Both men will be fighting over the One Nation vote and Mr Clarke's supporters will feel their man is best placed to secure it.

But Sir Malcolm refused to back down. Just hours after Mr Clarke and his supporters gathered at Westminster's St Stephen's Club, Sir Malcolm unveiled his campaign team and declared he would run.

"I am a serious candidate, I will be a candidate I suspect one or two of the other people whose names have been mentioned will not at the end of the day be standing."

Sir Malcolm said: "If you do believe that you need a combination of the One Nation tradition, but also against the European single currency and with a firm, robust view on Europe, then I would obviously think of myself as preferable to Ken Clarke because of his views on Europe," he told Sky News. "That is the kind of choice that needs to be made."

Sir Malcolm's campaign team includes two MPs who backed Mr Clarke in the last Tory leadership contest - Jacqui Lait and Peter Bottomley.