Michael Howard, the Tory leader, said today that the Conservatives saw "very considerable difficulties" in a police proposal that would allow them to hold terrorism suspects for up to three months without charge.

The proposal was on the table this morning as Tony Blair met opposition leaders at Downing Street this morning to garner cross-party support for tougher anti-terror legislation.

Mr Howard, accompanied by David Davis, the Shadow Home Secretary, told reporters after the meeting: "There’s a great desire at a time when the country faces such great danger to work together. We are all in this together and we all believe it is very important to show that the country is united in its response to the danger we face."

But he said the Tories were not comfortable with a proposal from the Association of Chief Police Officers that would prolong to 90 days, from its current maximum of two weeks, the time that police could hold terror suspects for questioning.

"So far as the three-month period of detention which the police have asked for, we see very considerable difficulties in that. That is a long time to hold someone without charge, and possibly just release them after that."

Charles Kennedy, the Liberal Democrat leader, said he understood the problems that the current limit posed police.

"The sheer extent of the carnage makes it very difficult. To collect evidence you can analyse within two weeks is scientifically very difficult," he said. He declined to say what the revised time limit should be.

The death of more than 50 commuters in four co-ordinated suicide bomb blasts on the London Underground and a London bus on July 7, followed by abortive copycat attacks last week, mean the major parties are keen to reach consensus on new anti-terror measures before Parliament sits again in October.

Mr Howard said that the Prime Minister had given his assurance that Parliament would be recalled from summer recess if necessary.

But the proposal to extend the questioning period will prove controversial. Paul Whitehouse, former chief constable of Sussex Police, told BBC Radio 4's Today programme: "I would be wary of any extension in that direction.

"Our experience with that in Kenya in the 50s and Northern Ireland in the 70s shows that there’s every possibility that if that’s exercised wrongly you can fuel the fire of terrorism. It’s a very tight rope to walk."

He added: "Intelligence is the key. We should be making sure we have sufficient resources to use existing people we’ve got, and work at ensuring that the public give us the information we need."

This morning's meeting was also due to discuss a proposal to allow police and security forces to use phone tap evidence in court - an idea to which Mr Blair has now given his backing, but which security agencies fear could compromise their operations and expose their techniques.

Sir John Walker, a former head of defence intelligence and a former deputy chair of the Joint Intelligence Committee, said that nobody wanted to fight the battle against terrorists "with one hand tied behind your back".

But he added: "The people in the security services are going to be conscious that they don’t want to blow methods and sources."

Sir John also said that British security forces’ focus on the IRA during the 1990s allowed Islamic terrorists to flourish, to the point where "London became the home for extremist groups worldwide."

Professor Paul Wilkinson, a terrorism expert at the University of St. Andrews in Scotland, told the BBC: "We took our eyes off the ball in the 1990s when al-Qaeda was building up its network. It wasn’t seen as a serious threat. We were of course preoccupied with the Northern Ireland situation. We have entirely reversed that policy since 9/11."

Mr Wilkinson said that a greater analytical focus on terrorist groups in the 1990s might have led to aviation security awareness that could have stopped the September 11 attacks on New York.

There is already cross-party support for a package of new criminal offences, including incitement and glorification of terrorism, that will be pushed through when Parliament resumes. Under that legislation, the Home Office will create a database of those engaging in "unacceptable behaviour" - including preaching hatred of the West - to make it easier either to prevent hate clerics from entering Britain or to deport them.

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