He said he wants current rules, which mean terror suspects have to be released if they are not charged within 28 days, to be changed in light of a “mounting” threat.
“This is not just a matter that should be left open – it has got to be decided by parliament,” he told the Home Affairs Select Committee.
The Government has said it wants to reopen the debate over the 28-day limit because of the complexity of terror investigations, which can involve suspects and leads in multiple countries.
Sir Ian admitted there has never been an occasion where detention beyond the current limit – doubled from 14 days over a year ago – was necessary, but felt it would happen soon.
“The prospect that we will need more than 28 days some time in the not-too-distant future is so real a prospect that parliament needs to consider it,” he said.
Concerns have been raised that extending the current detention period to up to 90 days could damage police relationships with the Muslim community.
The committee’s chair, Keith Vaz MP, asked Sir Ian if he accepted that an extension would “disproportionately affect” Muslims.
Sir Ian said it would certainly “not ease” relations, and conceded that he didn’t know of any bodies representing the Muslim community that would be in favour of an extension of the detainment period.
However, his claims over the increasing terror threat were supported by Lord Carlile, the government’s independent reviewer of terrorism laws.
“There is no question that there is an increased threat,” he said. “It is a good time to carry out a complete review of these powers.”
Lord Carlile, who supported the government’s abortive plans for a extended 90-day limit in 2005, said “almost nobody” would be held for the full 90 days.
“My estimate is that over the next five years there will be two or three cases that [would] benefit from an extension of the 28-day period.”
Last month the director of human rights group Liberty branded Carlile an “enthusiastic public champion for internment” over his support for extended detention periods.
Since the extension to 28 days in 2005, 204 people have been arrested under terrorism legislation – only 11 of which were held for more than 14 days. Eight were eventually charged.
