'Devastating blow' to terror plans

Director of Public Prosecutions Sir Ken Macdonald said prosecutors were satisfied with the present situation and were not seeking any extra time.

And Lord Goldsmith revealed that he would have quit as Attorney General in 2005 if Tony Blair had succeeded in getting a 90-day limit introduced and said he had seen no evidence for a change.

Critics of the controversial bid to harden the anti-terror laws dubbed the evidence given by the two men to MPs as a "devastating blow" to Gordon Brown.

But the Prime Minister's spokesman insisted there remained a "case for considering an extension" - with the Government widely tipped to propose a move to around 56 days.

Sir Ken, who is head of the Crown Prosecution Service, told the home affairs select committee investigating the need for tougher terror laws that 28 days had proved "useful and effective".

Asked if he would like to see it extended further, he said: "It is a matter of record that we have not asked for an increase. We are satisfied with the position as it stands at moment."

While there might be "respectable arguments" for an increase, he added, "our experience has been that 28 days has suited us quite nicely".

He gave his evidence shortly after Lord Goldsmith, who stepped down from the Government when Mr Blair left Number 10 in June, said he had seen no evidence to back an extension - even in the investigation of the alleged airline terror plot most often cited by supporters of the policy.

"Although the decision went up to the wire, having looked at this very carefully with the Crown Prosecution Service and the police, I was not persuaded that those episodes showed that 28 days was insufficient and I did not subsequently see any evidence during my time...to indicate that longer than 28 days was necessary," he told the committee.