Public safety could be at risk unless urgent reforms are made, the Chief Inspector of Constabulary has said.
In his annual report Sir Thomas Winsor also branded the criminal justice system "dysfunctional and defective".
"Bold and long-term decisions" were needed to improve policing and forces need to work closer together, he said.
The Government said it was "working hard to address pressures" on the justice system.
In his annual assessment of policing in England and Wales, Sir Thomas said there had been a 19% drop in police funding since 2010-11.
"There are indications that some forces are straining under significant pressure as they try to meet growing complex and high-risk demand with weakened resources", he said.
His proposals to improve policing included "considerable investment in technology to keep up with and get ahead of emerging online offending".
It comes after Met Police Commissioner Cressida Dick said too many crimes are being left unsolved.
During a speech about the future of policing in England and Wales, Cressida Dick admitted that national detection rates for some offences were "woefully low".
She added: "The courts are emptying, not filling. It is not good and I am not proud of it."
Sir Thomas also said rehabilitation of criminals needed to be taken more seriously, with people released from prisons being "guaranteed proper support" in dealing with benefits and finance.
In the report, Sir Thomas added that there was "continued controversy" about the 43-police force structure in England and Wales.
He also said there was a need for the police service to function as part of a single law enforcement system.