The Conservatives and the Liberal Democrats have called for an inquiry into allegations that hundreds of lawyers are bugged on prison visits.
An inquiry is under way into claims of bugging at Woodhill Prison
The Daily Telegraph, quoting an unnamed source, said conversations between prisoners and their lawyers were routinely being recorded across the UK.
The Ministry of Justice said monitoring was a police matter.
An inquiry is under way into earlier claims that a Labour MP's visits to Woodhill prison were secretly recorded.
Counter-terrorism officers are said to have secretly recorded MP Sadiq Khan's conversations with a constituent - terrorist suspect Babar Ahmad - in the Buckinghamshire prison in 2005 and 2006.
His case sparked controversy because it was suggested it may have been in breach of the Wilson Doctrine which bars the bugging of MPs.
Infringement of rights
The Daily Telegraph report claims that as well as terror suspects, murderers and category A prisoners being held across Britain were also being targeted for recordings.
Shadow home secretary David Davis said he was writing to the Justice Secretary Jack Straw demanding a full-scale investigation and said ministers must have been aware.
"It is inconceivable that this action has taken place without ministerial approval," he said.
"Whilst there can be reasons for eavesdropping on legal meetings, it is such a serious infringement of people's rights that there has to be a very good reason.
"It can put the trial at risk which means that serious crimes may go unpunished."
Liberal Democrat home affairs spokesman Chris Huhne said if the latest allegations were true, fundamental legal procedures have been breached.
"We need an immediate inquiry into exactly what is going on.
"If that confirms these allegations, I think it's the most astonishing and foolish policy that is going to prove to be totally counterproductive and quite calamitous."
Senior British lawyer Geoffrey Robertson QC said if the claims were true, they could lead to violent offenders being released.
"The end result... 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 told BBC Radio 4's Today programme.
Labour MP Andrew MacKinlay said: "The only surprise I have is that people are surprised.
"I and others have tried to draw attention to the abuse of powers by senior police officers over recent years, often only to be mocked.
"In my view this indefensible situation arises from the cocktail of supine ministers and the total absence of any Parliamentary oversight of the security and intelligence services."
Former High Court judge Sir Christopher Rose, the chief surveillance commissioner, has been asked by Mr Straw to conduct an inquiry into claims made about Mr Khan.
A Ministry of Justice spokeswoman said Sir Christopher would report back in due course.
She added that police monitoring operations were a matter for the police and were undertaken in line with the Regulation of Investigatory Powers Act 2000.
The Prison Service might grant the police permission to operate in prison providing there were no concerns about order or control and such co-operation was vital in the fight against serious crime and terrorism, she said.
"It would not usually be appropriate for the Prison Service to question the authorisations granted to the police to monitor an individual; nor would it expect the police to share details of the intelligence cases underpinning its monitoring operations," she said.