A major corruption inquiry has been launched into the Crown Prosecution Service and the organisation's headquarters at Ludgate Hill, London has been raided by detectives from the National Crime Squad.
The most serious breach of security involves the names of 33 "resident informers" - inmates who pass information from prisons to the police - which was believed to have been extracted from CPS computer files.
Those on the list, the most vulnerable of all informers, were alerted by the police and some were moved to other prisons. A number of enquiries were terminated to protect the men, and police sources say the leak has "greatly diminished" their chances of recruiting informers in the jail system.
The National Crime Squad was called in to investigate after detectives received intelligence that prominent criminals had obtained confidential material about prosecution cases. A surveillance operation resulted in the arrest of three men, one of them a clerk with CPS.
On Saturday the Attorney General John Morris failed in the High Court to prevent publication of details of the corruption allegation.
Mr Justice Gage, rejecting the Attorney General's argument, said: "Public interest demands, where there has been alleged corruption in the Crown Prosecution Service, it should be published, so that informants and future informants are made aware of the risk."
Senior CPS administration officer Mark Herbert, 30, was arrested at his home in Twickenham, west London, on allegations of passing details of cases to 40-year-old Kevin Sumer, a nightclub bouncer from Brentford, west London.
Both men have been charged and remanded in custody until 23 October. A third man was arrested and released on police bail.
Senior CPS staff were informed about the corruption claims by the police and had helped in the subsequent investigation. The CPS central case work department, which deals with serious criminal cases, was one of the sections looked at in detail by the enquiry.
Earlier this year, in a separate development, a National Audit Office report accused the CPS of being over-bureaucratic, slow and inefficient. The director, Dame Barbara Mills, resigned before the report's publication.