The BBC's Jane Peel: "The CPS has announced it has already put its house in order"

In a report published on Wednesday, Judge Gerald Butler attacked the agency's decision making system, and made several recommendations to improve accountability.

The judge said all decisions in such controversial cases should be made by a clearly identified person at a senior level. Any decision not to prosecute should be sent for reconsideration by Senior Treasury Counsel.

Confusion over responsibilities

The role of the former Director of Public Prosecutions, Dame Barbara Mills, also came in for criticism, with Judge Butler saying confusion over who was actually responsible for taking decisions whether to prosecute police officers had led to a "thoroughly unsatisfactory situation".

Judge Butler expressed "unease" over the current system, whereby the police report deaths in custody to the CPS and investigate them.

He said it was not part of his inquiry to make recommendations on that particular issue, but he regarded the matter of "such importance" that he had to flag up his concerns.

He also called for the CPS to give serious consideration to publishing its reasons for deciding not to prosecute police officers in cases involving deaths in custody, especially where an inquest jury had returned a verdict of unlawful killing.

Richard O'Brien died in police custody

He has looked at 15 separate decisions not to prosecute over deaths in police custody.

One high profile case involved Richard O'Brien in 1994.

Mr O'Brien, 37, was arrested on suspicion of being drunk and disorderly in Walworth, south London, in April 1994.

He lost consciousness while at a police station and was dead on arrival at King's College Hospital.

His wife Alison has fought for nearly four years to try to have the police officers involved in his arrest prosecuted.

In 1995 an inquest recorded a verdict of unlawful killing and the coroner called on the police to look into their methods of restraint and training.

The Crown Prosecution Service admitted the original decision not to press charges was flawed, and three officers were later charged with manslaughter.

Officers acquitted

They were subsequently found not guilty at trial.

There have been numerous other cases of people dying in police custody in recent years.

Last year the Crown Prosecution Service reaffirmed its decision not to prosecute police officers over the death of Shiji Lapite, a Nigerian asylum seeker.

The Crown Prosecution Service has already implemented many of the recommendations in the report

Mr Lapite, 34, died after a struggle with police in Stoke Newington in December 1994, and was found by an inquest to have been unlawfully killed.

However, after re-examining evidence, the CPS upheld its original decision that no action would be brought.

A spokesman said at the time: "In the absence of evidence to show that the actions of the police officers either singly or in concert were a substantial cause of Mr Lapite's death, there is not a realistic prospect of conviction."

At the inquest one police officer admitted kicking Mr Lapite in the head. He was found to have up to 45 injuries, and died from asphyxiation after being held in a neck-hold.

Call for independent checks

Deborah Coles, co-director of Inquest, the charity which campaigns for the families of people who die in custody, said the report added weight to calls for the independent investigation of such deaths.

She said: "It is yet a further vindication of what Inquest and the families we work with have been saying about how the current system fails to ensure openness and accountability when dealing with police crime and misconduct."