Police forces will have to axe another 34,000 officers and staff under Tory plans for brutal post-election cuts.
It would take total police job losses to 68,000 since the Coalition came to power.
Top officers warned forces would be too short-staffed to carry out their legal duties and keep vulnerable people safe.
Shadow Police Minister Jack Dromey raged: “The sheer scale of this is staggering. At least one in six police officers will be cut from the line of duty.”
The Home Office insisted no final decisions have been made on police cuts beyond 2016.
In a letter seen by the Mirror, leading officer Sir Hugh Orde revealed forces already “planned reductions” of 6,000 front line officers, 4,200 staff and 250 PCSOs over the next two years.
It follows 16,000 officers and 18,000 staff axed since 2010.
But the Home Office told chiefs to expect a further 20% funding cut in the years to 2020.
Sir Hugh, president of the Association of Chief Police Officers, wrote: “If budgets were further reduced by 20%, it is not unrealistic to expect forces to lose another 34,000 posts.”
In a statement last night, ACPO confirmed the Home Office’s plans.
Chief Constable Douglas Paxton, its lead on finances and resources, said: “The Home Office have advised us to make an assumption that the police service will face further funding cuts, and we should assume a cut of 5% in real terms per year – or a further 20% over four more years.
“It seems likely the service will therefore lose around another 34,000 officers and staff jobs in the period.”
Home Secretary Theresa May has claimed axing great swathes of the police force had made no negative impact on crime statistics. But a damning report this week revealed a fifth of all reported crime was missed off the official figures.
And Sir Hugh warned the next round of cuts would have a far more serious impact on front line policing.
He wrote: “A greater number of officer posts would be involved, and this could potentially have serious implications for statutory responsibilities and the safeguarding of the most vulnerable.”
Tony Lloyd, Greater Manchester police and crime commissioner, said such cuts were “not sustainable.”
He warned: “Britain has a reputation as a pretty safe place to live. You’re talking about putting that in jeopardy.”
And Steve Evans, of the Police Federation, added: “Officers are working at near-breaking point.”
Labour has pledged to save 1,100 police officers’ jobs if it wins the election.
There are 127,909 police officers in England and Wales and 64,097 staff.
A Home Office spokesman said: “Police reform is working and crime has fallen by more than a fifth under this government according to the independent Crime Survey.
“There is no question police still have the resources to do their important work and forces have demonstrated they are successfully managing to make savings while protecting the frontline and delivering reductions in crime.
“It is for PCCs to set the local policing priorities on behalf of their communities and for Chief Constables to take operational decisions about the use of local resources.”