Falconer dismisses detention plan

Lord Falconer said that since Tony Blair's 2005 defeat over a 90-day detention period - which he supported - prosecutors had adopted new procedures that meant they did not require an extension beyond the current 28-day maximum.

His intervention comes amid signs of a growing Labour backbench revolt on the issue, and follows public statements from Director of Public Prosecutions Sir Ken Macdonald and former Attorney General Lord Goldsmith that they see no need to go beyond 28 days.

Lord Falconer said prosecutors were now applying a lower threshold of "reasonable suspicion" to bring charges against terror suspects within the 28-day deadline, and then allowing investigations to continue to build the case to the higher standard required for a court trial.

He told BBC Radio 4's World at One: "If it is not necessary because you don't need it to fight terrorism effectively, then you shouldn't do it. I strongly believe that the debate about should it be 28 days, 42 days or 90 days has moved on because of the threshold standard. We should recognise that we have addressed effectively the question of the time it takes to investigate."

Mr Brown and Home Secretary Jacqui Smith argue that the police need more time to carry out inquiries into terror plots because of the complicated nature of the cases. They have the backing of the Association of Chief Police Officers.

But Lord Falconer, who was in charge of the legal system under Mr Blair's administration, said the time pressure has been lifted by the new lower threshold, which has been used in almost all terror cases over the last two years.

Under the new system, prosecutors no longer have to wait until they are confident that they have a 50% or more chance of securing conviction before pressing charges, said the former Lord Chancellor.

He told The World At One: "Many of the terrorist plots being investigated are complicated, involve the study of computers and inquiries abroad. That takes time - often longer than 28 days or 42 days or 90 days.

"The prosecution service have developed a way of dealing with that. If there is reasonable suspicion, and if you anticipate the evidence will get there, then they are allowing charges to be laid before they have got to that 51% or more chance of success which is the normal level before you charge."