Moves to extend the amount of time a terror suspect can be held without charge are the result of "political machismo", according to the Conservatives and Liberal Democrats.

Shadow home secretary David Davis and Lib Dem spokesman Nick Clegg told the Commons home affairs committee on Tuesday that there was no evidence for increasing the current pre-charge detention limit of 28 days.

Lib Dem leadership hopeful Clegg said the "case has not been made" for the government to press ahead with its "excessive, illiberal intentions" to increase in the limit of detention without charge.

"No real evidence has been presented to suggest that a change in the law is necessary," he argued.

Describing it as "vexed political issue", he told MPs it was "perplexing that the government is charging ahead" with re-opening the debate.

In 2005, Tony Blair suffered his first Commons defeat as prime minister when he attempted to push through legislation to increase the limit to 90 days. MPs instead opted to double the limit to 28 days.

The debate has returned under Gordon Brown, with ministers expressing a preference for doubling it again to 56 days, coupled with extra judicial and parliamentary safeguards.

Rhetoric

Clegg welcomed a "significant rhetorical change" in the past two years but said he was "not sure if I can see anything in the substance which would not have been proposed by the previous prime minister".

"It is not reasonable for the government to expect this parliament to legislate on a delicate issue which strikes at the heart of what the rule of law is all about," he argued.

Pointing to post-charge questioning and allowing the use of intercept evidence in court, he said there are "other measures we could take rather than re-opening the 28-day debate".

"I start from the position of profound scepticism about the need to focus on this single issue," he said.

Clegg also warned against allowing extremists to propagate "their values", adding: "Proceeding for policy without evidence exacerbates the feeling of alienation."

And he called on the government to "invest political capital in working with us rather than going down a cul-de-sac characterised by political machismo rather than cool headed evidence".

Intelligence

Davis also stressed the need to act on intelligence, "challenge the evidence and explore every possibility that doesn't erode liberty".

Talking of the need to balance security and liberty, he said: "My view is really very straightforward. Firstly, there is a real threat. Secondly, our attempt to deal with that threat places us between a rock and a hard place.

"Political machismo will not defeat the global terror threat."

He added: "We need to find holes in the state's defence against terrorism and plug those holes."

Warning of the "extent to which" the Muslim community feel legislation is "focused on them", Davis added: "There has never been a case where we can defeat terrorism unless we take the communities that terrorism operates in."

And he said he was "the author" of proposals to allow post-charge questioning.

"We have been through a whole series of exercises in the past year... and have come to the conclusion that there are a large number of alternatives to take away the pressure from 28 days," he argued.