Top barrister claims hundreds of violent criminals could be freed after bugging revelations

Violent offenders could be allowed to walk free in the aftermath of the prison bugging row, according to a leading barrister.

Geoffrey Robertson said the courts might release criminals if it was shown their meetings with lawyers had been taped by the police.

The QC spoke out amid calls for an inquiry into claims lawyers' legally-protected conversations with clients in jail are routinely bugged.

Justice Secretary Jack Straw has already launched an inquiry into claims a Muslim Labour MP's jail meetings with a terror suspect constituent were bugged at Woodhill Prison, Milton Keynes.

Sadiq Khan's case sparked particular controversy amid suggestions it breached a ban on bugging MPs - and is being examined by Chief Surveillance Commissioner Sir Christopher Rose.

Now the Tories and Liberal Democrats are demanding a fresh probe into claims by an unnamed whistleblower that it was part of a wider practice nationwide.

Defence barrister Mr Robertson said there needed to be an immediate investigation into the claims - warning that if true they could lead to violent offenders such as Huntley being released.

"The end result, if that is the case, is that these cases will have to be brought back to court and in my view the courts will react with such fury as a matter of principle, those whose conversations were bugged will have to be let out," he said.

Murderers and other category-A prisoners - including Soham murderer Ian Huntley - were said to have been targeted as well as terror suspects.

Opposition parties said such a practice would strike "at the heart" of the justice system and suggested it could only have been sanctioned by ministers.

The Ministry of Justice said covert listening operations were "a matter for the police and are undertaken in line with the Regulation of Investigatory Powers Act 2000".

But Shadow Home Secretary David Davis said the allegations were so serious they merited a new inquiry.

"If it is... a widespread practice it is very hard to imagine that could have happened without ministerial approval because the risks are so great - it goes so close to the heart of our justice system and it puts the whole trial process at risk," he said.

"That is why I have called for Mr Straw to set up a second inquiry - not to stretch the first one, we need the answer to the Rose inquiry in a couple of weeks' time - to actually establish what the real practice is, how common this is and what needs to be done about it."

Joining the calls, Liberal Democrat home affairs spokesman Chris Huhne said it would be "appalling" if the practice was so widespread.

"Not merely because it offends against one key principle on which the legal system has been based but also appalling because it is going to be totally counter-productive - the idea that this would not get out is absolute madness."

Police sources say dozens of sensitive bugging operations on prisoners have been shelved as a result of their bugging methods being made public.

They insist the surveillance operation on MP Mr Khan and his constituent was lawful and 'fully justified'.