Brown attacks Tory rebel as ex-Sun editor says he'll fight seat

In a bid to exploit Conservative disarray over Mr Davis's impending resignation, the Prime Minister used a Downing Street news conference to declare that the affair was proof the Opposition was as divided as ever.

Mr Brown gave the clearest signal yet that Labour will not put up a candidate in Mr Davis's York-shire constituency of Haltemprice and Howden, declaring: "I think everyone now recognises that this is a stunt that has become a farce and has revealed the deep divisions of the party."

Ex-Sun editor Kelvin MacKenzie today said he was "90 per cent certain" to stand against Mr Davis if Labour failed to take part in the byelection that is expected on 10 July.

But the former shadow home secretary, 59, hit back at the Prime Minister and taunted him for being "cowardly" over his plans to extend detention without charge to 42 days for terror suspects. He also welcomed the chance to take on Mr MacKenzie. "Bring it on, we will take on [Rupert] Murdoch's money," Mr Davis said.

The Tory MP, who has quit the Shadow Cabinet, was forced to admit his frontbench career may be over. Asked if he had effectively thrown it away, he told Radio 4's Today programme: "That may well turn out to be the case. We are a party, not a regiment, and we are in politics for reasons of principle. And to carry this out requires a degree of risk or sacrifice."

Seeking to drive a wedge between the popular reaction to his cause and that of commentators, he said: "The Westminster village fusses about who's up and who's down, but frankly this is trivial compared to what has happened to 800 years of liberty in just a decade."

The Liberal Democrats, Ukip and BNP said they would sit out the by-election. The Monster Raving Loony Party pledged to put up a candidate called Madcow girl.

Mr MacKenzie said media tycoon Mr Murdoch had encouraged him to stand and was willing to bankroll his campaign. The Sun supported Gordon Brown's counter-terrorism laws strongly.

Mr MacKenzie said: "It's not a publicity stunt. The Sun has always been very up for the 42 days, or perhaps 420 days, frankly.

"I don't view my civil liberties as being at risk but I do view my life being at risk if I'm on the Tube or the train and some bad guy wants to blow me up or my family up. I don't feel constantly threatened by CCTV, I don't feel worried by ID cards, I'm happy to produce my driving licence everywhere I go.

"If I'm not doing anything wrong, I don't feel I'm under any kind of threat."

Mr Davis had hoped to lead a by-election battle against the Government over civil liberties. He said: "If the Labour Party chooses not to defend its policies, if they choose not to take part in the democratic process, they are going to show they are ashamed of their policies and frankly it's contemptuous of the British electorate."

However, there was a furious Tory reaction to Mr Davis's move. Former deputy prime minister Lord Heseltine said he had given up his chance to influence Tory policy: "To throw it all away for a byelection - it will prove nothing."

Sir Patrick Cormack was the first Tory MP to publicly criticise Mr Davis, calling the by-election a "colossal misjudgment". For Labour, Communities Secretary Hazel Blears said the Tories were like "ferrets fighting in a sack".