The criminal justice system is in danger of "meltdown" because of Government spending cuts, a coalition of unions has warned.
Coming together for the first time to address the Government's "slash and burn" policy, the unions said public safety was being put at risk, with the police, courts, prisons and probation service facing "irreparable damage".
Crime will go undetected, court proceedings will experience long delays and prisoners will not be given the chance to rehabilitate, they said.
The Police Federation of England and Wales, probation union Napo, Prison Officers Association and the Public and Commercial Services union - who together represent 210,000 staff in the justice sector - said they were joining forces to show how cuts were having an effect across the board.
Speaking in Westminster at a meeting of the Justice Unions Parliamentary Group, Julie Nesbit, chair of the constables' central committee at the Police Federation, warned that a 20% cut in the police budget would damage frontline services.
She said: "The police service faces the biggest threat for generations. With such severe budget cuts there can only be one winner, the criminal, and there can only be one loser, the public."
She attacked the timing of the Government's cuts, which come during the financial crisis, when crime is likely to be going up, and also ahead of the London Olympics, "the biggest policing operation this country has ever faced". She added: "This is a just a slash and burn policy without any regard for public safety."
Ms Nesbit also accused Theresa May of ignoring the wider role the police play in dealing with vulnerable young people, drug users and people with mental health problems. She said: "The Home Secretary should understand what we all know, that the police are the catch-all emergency service who everyone defaults to when the nature of the crisis is unclear. We need to know who will deal with these incidents if this is no longer a job for the police."
A Ministry of Justice spokesman said: "We are committed to reforming our public services and reducing the cost of the justice system while protecting the public and punishing those who break the law. This Government inherited a system of spiralling costs, overly complex procedures and ineffective sentencing provisions.
"It is crucial that we modernise - our courts must reflect changes to our population, legal aid should only go to those who need it most and offenders must face swift justice. We believe that payment by results will help us identify the best ways to cut offending rates and bring about a long-lasting reduction in crime."