Police numbers have been slashed to "dangerously low" levels, the five most recent heads of Scotland Yard, the country's biggest force, have warned.
Cuts of more than 30,000 officers and support staff have led to "the feeling of lawlessness generated by knife murders", the former Met Police chiefs say in a stark message.
The five write in The Times: “The reduction of police and support staff by more than 30,000, the virtual destruction of neighbourhood policing and the inadvisable undermining of lawful police powers such as stop and search, have taken their toll.
"Common sense suggests that these factors have contributed to the feeling of lawlessness generated by knife murders and ‘county lines’ drugs.”
The letter is signed by Lord Condon, Lord Stevens, Lord Blair, Sir Paul Stephenson and Lord Hogan-Howe, who ran the Met from 1993 to 2017, as well as three other senior officers.
Their warning comes on the same day that the chief inspector of constabulary says public safety could be put at risk unless “profound and far-reaching” police reforms are urgently introduced.
In his annual assessment of policing in England and Wales, Sir Thomas Winsor said, if changes are not made, forces “face unacceptable compromises in quality of service levels of public safety”.
The former police chiefs say the next prime minister will inherit a police service that "has had its resources drained to dangerously low levels.”
They added: “Police and crime commissioners, however well motivated, do not have the skills or resources to address the emasculation of British policing experienced in recent years.
"If they become victims of crime, the public have perilously low expectations of the police today.
“This cannot be acceptable in our modern, diverse democracy. It is the first duty of any government to protect its citizens from harm.
"The responses to terrorism, cybercrime and the restoration of police resources and confidence cannot be provided by a fragmented system comprising more than 40 territorial police forces.”
One of those potential prime minister's, Boris Johnson, has conceded it will be a "stretch" to fulfill his latest commitment to recruit an extra £20,000 police officers within three years,
In his report for Her Majesty’s Inspectorate of Constabulary and Fire and Rescue Services (HMICFRS), Sir Thomas called on police chiefs and politicians to make “bold and long-term decisions” to improve policing.
He said: “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.”
In the report, which looks at the state of policing between April 2018 and May 2019, Sir Thomas said: “I believe some profound and far-reaching aspects of police reforms are called for."
There has been a 19% drop in police funding since 2010/11.
In 2018/19, police funding amounted to £12.3 billion with a workforce of around 122,000 police officers and 68,000 police staff. This was around one police officer for every 480 people, according to the report.
In his findings, Sir Thomas said also branded the criminal justice system as “dysfunctional and defective” as he said prison rehabilitation plans and support for inmates once they were released needed to improve.
Policing minister Nick Hurd said that funding for police has increased by more than £1 billion this year, including council tax and money to tackle serious violence.
“Police and crime commissioners have already indicated they plan to recruit over 3,500 extra officers and staff," he said.
“We also recognise there are wider pressures on the criminal justice system and the Government is working hard to address these.”