Labour will announce on Monday that the party will not contest David Davis's seat – in an attempt to embarrass the Conservative leadership and highlight their "soft" stance on terrorism.
Ministers lined up to deride Mr Davis's decision to resign and fight a by-election in his East Yorkshire seat on 10 July.
Jacqui Smith, the Home Secretary, accused the Conservatives of being in "total disarray" and said they needed to "come clean" over what had happened.
"Faced with a crucial decision on the safety and protection of the British public, the Conservatives have collapsed into total disarray on what is their first big policy test since they have come under greater scrutiny," she said.
Jack Straw, the Justice Secretary, branded Mr Davis's behaviour "odd", adding that David Cameron had treated the decision like "a piece of stinking fish".
Mr Brown used a monthly press conference at Downing Street before Mr Davis's announcement to attack the Conservatives for failing to engage in a national consensus on the need for tougher powers.
"I believe they will regret their action in failing to support action necessary in our country to deal with both the causes and the problems associated with terrorism."
But the Liberal Democrat leader, Nick Clegg, gave Mr Davis his backing after being telephoned by him late on Wednesday. The Liberal Democrats will not be fighting the seat although they came second at the last election.
Mr Davis has decided to sacrifice his job as Shadow Home Secretary to fight the by-election after Gordon Brown's nine-vote victory on the proposal to extend pre-charge detention from 28 to 42 days for terrorist suspects. Mr Cameron replaced Mr Davis with Dominic Grieve.
Mr Davis said that, after it became clear that Mr Brown had won the vote, "not even the Angel Gabriel" could have persuaded him to drop the idea.
As he planned a three-week campaign, promising to trigger a debate on a different issue each week, his private office at the Commons was taking dozens of calls from members of the public with pledges of support. But many Tory MPs were privately uncomfortable voting against the Government on tougher terror laws and some were keen to avoid being accused of being "soft on terror".
Mr Davis said "a significant minority" of Tory MPs thought he was "mad' to push for the Conservatives to oppose the Government's anti-terror laws. He admitted Mr Cameron had to be persuaded about his tactics but said Mr Cameron had been won round, and praised Mr Davis's lead on the issue.
"David and I have virtually identical views on most of these issues. I think he was pretty much onside on the philosophy and the strategy but unsure of the tactics. He was persuaded of the tactics in the end," said Mr Davis. "I am running as a Conservative but I will be seeking to build a cross-party consensus on the issue. I will be seeking to go wider than politicians," said Mr Davis who expects a number of high -profile celebrities to join him.
Mr Cameron and Shadow Cabinet ministers will go to his Haltemprice and Howden seat for the campaign. He is defending a majority of 5,116 but it is unlikely the Tories will pour in the resources they devoted to winning the Crewe and Nantwich by-election.
"The public can change its mind on these issues. I am not going to turn around the public's opinion in three weeks, but what I will do is raise the salience of these issues," said Mr Davis.Reuse content