There are fears about other clerics

Lord Carlile, the peer who is the official reviewer of UK terrorism laws, also said there could be 20 clerics like Abu Hamza al-Masri in the UK.

"Very little has been done in the past to look into... some imams," he argued.

He also told the home affairs committee the Iraq dossier affair had "had a devastating effect" on trust in MI5.

The peer stressed there were some "wonderful imams" but raised fears about those let into the UK in the past.

'Impressionable'

Radical cleric Abu Hamza was jailed last week for inciting murder and racial hatred.

In the wake of the case, Lord Carlile told the Commons home affairs select committee: "I would be amazed if there were more than 20 such clerics in the country - but that is a pure guess.

"My worry is that they are in places such as cities and custodial institutions where there are larger numbers than elsewhere of impressionable young men.

Lord Carlile says trust in terrorism warnings has been damaged

"A small number can have a disproportionate effect if they are in the wrong place."

He went on: "If you talk particularly to young female students in the larger, more rackety universities, there is a degree of concern expressed about some societies in these universities where women are excluded and where there might be radicalisation."

Lord Carlile is writing a report about the definition of terrorism which is expected to be handed to government in October.

Labour MP Shahid Malik argued against talk of "moderate" and extremist Muslims. Instead, it was better to talk of "mainstream" Islam to get a "sense of quantum".

Terrorism laws should also be aimed at all types of terrorism so Muslims did not feel they were being targeted, he said.

Escaping prosecution

The MPs are investigating the case made last year for extending the time limit on holding terrorist suspects without trial from 14 to 90 days.

The Commons opted for a 28-day compromise, but Lord Carlile is among those who believe there should be a 90-day limit.

He said he had been told by police outside London about at least one case where people had not been prosecuted because police did not have enough time to find evidence.

The case involved a "set of circumstances crossing the Anglo-Scottish border", and there were about eight suspects, he said.

"I have been told that there were people who ought to have been prosecuted and about whom it was thought they could be prosecuted if they had had enough time to gather evidence while they were in custody," he said.

"I was provided with a considerable amount of material and I was satisfied that that was the case."

'Dodgy dossier'

Human rights lawyers last week complained that Lord Carlile had argued for a 90-day detention period on the basis of secret information which the public could not see to make their own decisions.

The Lib Dem peer said public trust in warnings about terrorism had been "very damaged" by the controversy over the intelligence used to justify the Iraq war.

Without giving his own opinion on the intelligence, he said the "dodgy dossier" about Iraq's alleged weapons "had a devastating effect on the level of trust given to MI5".

Lord Carlile urged the government to do more to reveal the true nature of the terrorism threat.

Much of the information was in the public domain but people did not always know where to look at it.

The government should simplify a recent immigration judgement which gave details of the al-Qaeda threat, he said.

"This is one of the few things on terrorism legislation that the Americans are better at than us," added the peer.