Police must hold suspects longer than the current 28-day limit, Britain's senior adviser on anti-terrorism legislation said Monday.
Lord Carlile, the independent reviewer of counterterrorism legislation, said the maximum detention in each case should be decided by judges, not by Parliament.
Former Prime Minister Tony Blair had sought a 90-day limit, but parliament cut that to 28 days, double the previous limit.
"The fact is that the judgment on days is completely sterile. I would have thought that every civil liberties organization in this country and every person detained would be happy for their case to be considered by a senior judge on an evidence basis," Carlile said in an interview on British Broadcasting Corp. radio.
"That would be an intelligent basis for debate, not an entirely arbitrary one of days, which provides no intelligent foundation for the discussion," Carlile said.
Meanwhile, the second suspect charged in Britain in the failed car bombings in London and Glasgow faced a court appearance Monday.
Dr. Sabeel Ahmed, 26, who worked at Halton Hospital in Runcorn, northwestern England, is accused of possessing information that could have prevented an act of terrorism. He was charged within 14 days of his arrest.
Dr. Bilal Abdullah, 27, who worked at a Scottish hospital, was charged last week with conspiring to set off explosions. His alleged accomplice remains under guard in critical condition in a hospital where he is being treated for severe burns.
Another suspect, Dr. Mohamed Haneef, has been charged in Australia with providing support for a terrorist organization.
One other suspect is still in custody in Britain but has not been charged. Three others were released without charge.
Ken Jones, head of the Association of Chief Police Officers, said that although the investigation moved swiftly over the weekend, police will need more time in some cases.
"Let's get increased oversight mechanisms of some sort, then it's up to Parliament to talk about what an upper limit might look like," Jones said.
Lord West, the former navy chief appointed to oversee security issues in the Home Office, said police and security services are now monitoring about 30 groups with the potential to mount an attack within a short time.
"Effectively there are about 2,000 individuals who are being monitored in varying degrees of closeness and probably about another 2,000 loosely connected with them," West told the BBC.
He said police had come close to the 28-day limit last year before charging eight suspects in an alleged plot to bring down U.S.-bound airliners with liquid explosives.
West didn't say whether he thought Parliament or judges should set time limits, but said it was necessary to "insure that police and the security service are able to gather the sort of data they need to convict these people."
"I think now looking at the complexity of this there will be occasions when we will need more than 28 days," West said.
"We've seen the sheer complexity of data and things like that now that we have to crawl through. The people we are up against are cleverer and cleverer at hiding these things," he said.