Public confidence in the ability of police officers to do their jobs has been “severely dented” as forces struggle to cope with dwindling resources, parliament’s spending watchdog has warned.

The public accounts select committee concluded police are taking longer to charge suspects, fewer arrests are being made and the number of patrol officers has been stripped back.

Cuts in funding and reductions of about one-fifth to staffing levels have left forces under “increasing strain”, according to a cross-party report released on Wednesday.

The report highlighted how police are dealing with more non crime-related incidents, at a time when violent and sexual offending is on the rise.

It comes amid a heated debate over why crime is rising. The London mayor, Sadiq Khan, has led Labour politicians this week in claiming funding cuts are a major factor in the rise in knife attacks across the UK. Government ministers, in contrast, have blamed a change in the “nature of crime”.

The report said: “Forces are struggling to deliver an effective service: it is taking longer to charge offences, they are making fewer arrests, they are doing less neighbourhood policing and public satisfaction is declining.”

The committee cited figures showing the proportion of crimes resulting in a charge or summons dropped from 15% in March 2015 to 9% in March 2018.

Police are carrying out less proactive work, including fewer breathalyser tests, motoring fixed penalties and convictions for drug trafficking and possession, the report said.

MPs also levelled criticism at the Home Office, accusing the department of failing to show “strategic leadership” of the policing system and having only a “limited understanding” of the resources needed by forces.

“The police’s main duties are to protect the public and prevent crime,” the report said. “But only about a quarter of the emergency and priority incidents that the police respond to are crime-related.”

Meg Hillier, the chairwoman of the public accounts select committee, said: ‘The ‘thin blue line’ is wearing thinner.’ Photograph: Ray Tang/Rex Features

Meg Hillier, the chairwoman of the committee, said: “The ‘thin blue line’ is wearing thinner with potentially dire consequences for public safety. Public confidence and trust that the police will respond is breaking down.

“This cannot continue. Government must show leadership and get on with fixing the flaws at the heart of its approach to policing.”

A series of highly critical reports have prompted intense scrutiny of police performance and funding.

The number of arrests in England and Wales has halved in a decade, while recorded crime has risen across a number of categories, including homicide and knife-related offences.

Sara Thornton, the chairwoman of the National Police Chiefs’ Council, claimed last week that forces were too stretched to take on all “deserving” issues, such as logging misogyny reports.

Police funding has fallen by 19% in real terms since 2010, while officer numbers have decreased by more than 20,000 over the same period.

Pressure on ministers to provide a cash injection intensified after a warning from another Commons committee that policing risked becoming “irrelevant” amid vanishing neighbourhood presences and low investigation and detection rates.

While the recent budget included £160m for counter-terrorism policing, the government faced criticism from senior officers and some Conservative backbenchers over the absence of any commitment for general police funding.

Louise Haigh, the shadow policing minister, said Tory claims that the consequences of cuts have been exaggerated were in tatters.

“From rising crime to plummeting prosecutions and the horrendous impact on officer resilience and welfare, this report shows quite clearly that the government has finally broken the police,” she said.