Gordon Brown was quick to capitalise on Conservative discomfort over the resignation of David Davis, saying on Friday the security issue had exposed Tory divisions.

Seizing on what commentators called the first bit of good news he has had for months, the prime minister said Davis' decision to fight a by-election on the 42-days issue was a "stunt that has become a farce".

He was speaking as former Sun editor Kelvin Mackenzie revealed he may challenge Davis in the July 10 by-election in East Yorkshire.

"It has simply revealed the deep divisions in the Conservative Party," Brown said.

Davis, whose unprecedented decision perplexed fellow Conservatives, said: "I feel duty bound to make a personal stand against this assault on fundamental freedoms."

The Conservatives' spokesman on home affairs resigned his parliamentary seat on Thursday to stand again, promising to argue against what he called "the slow strangulation of fundamental British freedoms by this government."

The move, a personal decision not sanctioned by the Conservative leadership, effectively makes the vote in his east Yorkshire constituency a referendum on Brown's plans to toughen terrorism laws.

DAVIS "SLASHED HIS OWN PARTY'S JUGULAR"

But it failed to impress media commentators.

"Yesterday he slashed his own party's jugular instead of Gordon Brown," said the Sun.

"He will win praise from many voters glad to see a politician standing on a point of principle but in truth his vanity has led to an act of incredible selfishness."

The Labour-supporting Daily Mirror was delighted.

"If Cameron can't keep a grip on his party in opposition, how would he cope with the pressure of running the country," it said.

Now Mackenzie has provided the latest twist in the drama.

Asked whether it was Sun owner Rupert Murdoch who wanted him to stand, Mackenzie said "Yes it is."

"Rupert Murdoch and Rebekah Wade, who is editor of The Sun, both felt that democracy would not be best served by a walkover and suggested to me last night that I might be the person to fill the hole."

When BBC Today presenter John Humphrys asked him: "You don't always do what people tell you to, do you?", Mackenzie retorted "I do if it is Rupert Murdoch, strangely."

"Vote for me, I'm The Sun's man," Mackenzie told BBC Radio, insisting it was not a publicity stunt.

Mackenzie said he would not stand if Labour contests the seat, but later told BBC TV his instinct told him he would end up being a candidate.

Davis is defending a majority of over 5,000 in Haltemprice and Howden where a by-election will cost taxpayers an estimated 75,000 pounds in administrative costs.

The Liberal Democrats have already said they would not oppose Davis and Brown was dismissive about the move.

"We don't know whether Mr Davis is going to be a Conservative or an independent Conservative Party candidate," Brown said.

"What we know is that at the first test of what their policy is on the big central issue of national security, the Conservative Party are totally divided."