Home Secretary Charles Clarke may have endangered some of the most high-profile terrorist prosecutions yet seen in Britain, it was suggested yesterday.
In a bid to win backing for new terror powers, he distributed a seven-page Scotland Yard document which contained details of three terrorist cases - currently sub-judice.
The contents of the case studies cannot be repeated in full because they would amount to contempt of court.
But they included details of evidence against a number of defendants and their behaviour in police interviews.
Media lawyer Rod Dadak said: "I would be most surprised if, in issuing a release seeking to justify new detention powers, any reference would be made to a case which has yet to come to trial.
"It is inappropriate to do so and clearly calls into question the risk of prejudicing a fair trial."
He added: "The detail they have given impacts on the conduct of the defendants, which would appear to breach the rules with regard to contempt." One of the cases highlighted by Scotland Yard has been described by a senior legal source as the biggest terror prosecution mounted in the UK.
The Met's briefing note was drawn up by Assistant Commissioner Andy Hayman, who is in charge of the antiterrorist branch, in a bid to explain why police need powers to detain terror suspects for up to three months before charge.
The Home Office said the Crown Prosecution Service had cleared the material.
A CPS spokeswoman said: "It is the CPS's view that the material that the document contains is not prejudicial to any future proceedings."
A Home Office spokeswoman said: "There is no question whatsoever of the Home Office issuing material which might prejudice forthcoming legal proceedings."
The Home Office distributed the Met's document to MPs, peers and journalists.
Headings of each case study stated "This case is sub judice and it would therefore be inappropriate to release further details" but then went on to include information banned from publication ahead of a trial by the 1981 Contempt of Court Act. Meanwhile, Mr Clarke also published new plans to give police powers to temporarily close places of worship, such as mosques, which are being used by extremists.
The trustee or registered owner of a place of worship would be issued with an order - obtained from a court by the police - requiring them to take steps to stop such behaviour.
Failing to do so would be a criminal offence. If the activity persisted, police could apply to the court for a "restriction of use order" which could temporarily close all or part of the premises.
The consultation paper said the new powers would be a "last resort" and police would attempt to solve problems at any place of worship.
Controversial plans to make it a criminal offence to praise terrorist attacks were significantly watered down. Mr Clarke abandoned proposals which would have made it a crime to glorify terrorist acts.
The offence of glorifying terrorism will still feature in a new Terrorism Bill but it will have to be proved that the person making the statement intended to incite further terrorist acts.