Murderers, rapists and violent criminals could escape prosecution following a "bizarre" legal ruling.

The ruling, made by a district judge at Salford Magistrates' Court and backed by the High Court, means an end to the practice of releasing people on bail and calling them back for further questioning later - a common practice in most major inquiries.

Police forces can no longer put anyone out on bail for more than 96 hours without either being in a position to charge or release them.

After the four days is up, officers can no longer question suspects and can only re-arrest them if they have new evidence, the ruling says.

Police chiefs have been left baffled by the "bizarre" ruling and both the Association of Chief Police Officers (Acpo)and the Crown Prosecution Service are currently considering the ramifications for forces across England and Wales.

Sir Norman Bettison, former Merseyside chief constable and now chief constable of West Yorkshire Police, said: "This means unless this is overturned police can no longer put anyone out on bail for more than 96 hours without either being in a position to charge or release.

"It's on the verge of a disaster now because the question being asked by my custody sergeants is, 'What do we do, boss?'

"I cannot countenance turning people away from the charge office and telling them all bets are off and they are free to go."

Merseyside Police said that as of yesterday, there were 2,984 people out on bail across the county.

A statement by Acpo said: "This ruling has a profound impact on how the police have investigated crime under a legal framework interpreted and used during the last 25 years.

"Unless overturned, the indications are is that police can no longer put anyone out on bail for more than 96 hours without either being in a position to charge or release.

“We are working in partnership with colleagues across the criminal justice system, including the Crown Prosecution Service and Home Office, to determine a sensible way forward and seek to reduce any immediate impact.

"Chief officers have significant concerns as to the effect it will have on policing.”

Home Secretary Theresa May said: "I think this is a matter of great concern. We're working with Acpo at the moment and looking at a number of possibilities as to how we can advise the police on this issue.

"There may be an opportunity to appeal this decision. We are also looking at whether or not it's necessary to introduce legislation in order to deal with this issue.

"We are conscious of the concerns this judgment has brought in terms of operational policing."