Tory attacked Cameron after being refused a peerage

The Tory leader said that hours after he refused Ali Miraj's request, the would-be MP spoke out against him.

Mr Miraj, who claimed Mr Cameron was replacing 'substance' with 'box-ticking and gimmickry', was last night suspended from the Tories' priority list of potential candidates for the next election.

In the extraordinary public outburst, Mr Cameron also attacked other senior Conservatives who in the past few weeks have criticised his strategy for winning power.

He said the party would never be successful if it tried to 'cling to the past'. But his deepest scorn was reserved for Mr Miraj, who was previously a steadfast supporter.

Mr Cameron effectively accused him of political blackmail, saying he asked for, and was refused, a seat in the House of Lords on Monday, just hours before making the comments.

Mr Miraj refused to deny the blackmail claim, but accused Mr Cameron of a 'smear' campaign against him. He said: 'I'm not engaging in petty, playground politics and I am shocked that David Cameron has stooped this low.

'A private conversation should remain private. On his present behaviour, Mr Cameron is not fit to be Prime Minister. He clearly cannot take constructive criticism.'

Tory sources said Mr Miraj, who stood for the party in Watford at the last election, had suggested he become a peer so that he could act as a 'cheerleader' for the party.

Mr Cameron told Radio 4's Today programme: 'I think people will draw their own conclusions about someone who one day asks for a peerage, to be elevated to the House of Lords, and the next minute launches a great attack on the leader of the Conservative Party.'

At Westminster, some Tory MPs expressed surprise that Mr Cameron had become immersed in a row with a little-known party member.

Former frontbencher Mark Field said: 'This very public falling-out is preventing us from getting the proper airtime for the Conservatives' excellent new policies.'

But the Tory leader's aides insisted that he had been right to make public the discussions to put the attack 'in its proper context'.

There was no hiding their dismay, however, that Mr Miraj - an early backer of Mr Cameron's leadership bid - had joined Right-wingers in attacking his leadership style.

Mr Cameron, who is going on holiday to France next week, has been bruised by a dip in the opinion polls and internal conflict over grammar schools.

Labour sought to heap further pressure on Mr Cameron last night by fomenting speculation that Gordon Brown may capitalise on his recent poll bounce by calling a snap General Election as soon as October.

Party vice-chairman Martin Salter told the Times: 'We have been put on an election footing and preparations are under way so that we are ready for an election whenever the Prime Minister chooses to call it.

'The party has been put on alert for an early election that could take place as soon as this autumn.'

However, most Westminster experts believe that a 2008 election is a far more likely prospect.