The official police watchdog has said it is raising a "red flag" against the state of policing after a damning new report found a series of failings.
Her Majesty's Inspectorate of Constabulary (HMIC) found that victims are being let down, criminal cases shelved and suspects left untracked as police fail to carry out basic functions.
It also issued an unprecedented warning that a shortage of detectives and investigators amounts to a "national crisis".
"Over the last few years, HMIC has said consistently that police forces were managing well in increasingly difficult circumstances," said Her Majesty's Inspector of Constabulary Zoe Billingham.
"Nonetheless, today, I'm raising a red flag to warn forces of the consequences of what is, to all intents and purposes, an unconscious form of rationing of police services.
"We are leading to a very serious conclusion regarding the potentially perilous state of British policing in this report."
But some observers have pointed out that year on year, policing budgets have been cut.
"Serving officers and retired officers have been saying for years that the cuts implemented would lead to precisely this result," said Sky News police analyst Graham Wettone.
"This is no great surprise at all. It's becoming quite a stressful situation because of the pressures involved now, there are more pressures on police officers than ever before."
The report, which looked at forces in England and Wales, uncovered evidence of emergency calls being downgraded in order to justify a slower response and failings in responding to vulnerable victims.
Fewer arrests were made, a large number of crimes were effectively "written off", suspects were not always pursued and inexperienced officers were left to carry out complex investigations, the review found.
HMIC said it was also warning for the first time of a national crisis in the shortage of detectives and investigators in many forces.
This is leading to excessive workloads and complex investigations are being led by those who lack appropriate experience.
In one instance inspectors saw a uniformed officer investigating rape.
Overall, one force - Durham Constabulary - was judged to be "outstanding", 28 forces were "good", 13 "require improvement" and one - Bedfordshire - was rated "inadequate".
But Bedfordshire Police's chief constable Jon Boutcher hit back at the criticism, saying: "While I welcome the inspector's comments regarding the challenges we face as a force in regards to our complex demands and lack of resources due to poor funding, it is incredibly disappointing to have been so unfairly judged."
Brandon Lewis, the Minister for Policing and the Fire Service, said: "This Government has protected police funding, through the 2015 Spending Review.
"There can be no excuse for any force that fails to deliver on its obligations - those identified as inadequate or requiring improvement must take HMIC's findings very seriously and I expect to see rapid improvements."