The chief constable of one of England’s biggest police forces has said the reality of modern-day policing means the public sometimes do not get the service they expect.

David Thompson of West Midlands police said demands on the force were increasing, with cuts across all public services meaning more vulnerable people were coming into contact with the police.

Warning that the list of crimes that needed to be investigated, including modern-day slavery and gang crime, was increasing, he said it had left forces in an unsustainable position.

He told the BBC: “The level of calls we’re receiving this summer are very challenging … sometimes that service that we’re providing [at] those peak times doesn’t meet what the public expect.

“We may be dealing with it over the phone where they would like to see us, and I’m sorry about that but that is the reality of where policing is now. And on some occasions ... the service will not meet what I want it to do and it will not meet the response that the public absolutely will want when they’re at a time of vulnerability.”

He said the force was “drawing the bar higher” on what it would investigate, but stressed this did not refer to offences such as serious assaults.

Thompson, who is also finance lead for the National Police Chiefs’ Council, has previously said police forces faced hard choices as a result of the terrorism threat and rising cybercrime.

He said last year that the public might have to wait a bit longer for police to respond to non-urgent calls, and that just having to “manage the day job” had created “stretch”.

The West Midlands police and crime commissioner said it was an “inescapable conclusion” that cuts to policing were endangering the public. David Jamieson said fewer officers to deal with rising crime was a “deadly equation”.

Previously routine duties, such as officers visiting homes after a burglary or being present after a person had their car broken into, were becoming increasingly difficult.

Jamieson told BBC Radio 4’s Today programme: “This year, with the warmer weather, we have just been inundated by violent crime and we’re seeing homicides going up rapidly.

“The homicide team in the West Midlands is actually at bursting point at the moment, dealing with the many serious incidents they’ve had. Add to that the sexual and domestic crime which has been much more important in the public’s mind in the last one or two years.

“We really are at a point now where it’s extremely difficult to see how we can sustain what the public would call an acceptable level of policing.”

Asked if cuts to police funding in recent years were endangering the public, he said: “I think that’s the inescapable conclusion. And I leave your listeners to work this out. You know, we have far fewer officers, we’re not able to deal with all the incidents we could deal with. It’s a deadly equation, isn’t it?”

The Home Office has said total investment in the police system will be increased by over £460m in 2018-19, with West Midlands police receiving a cash increase of £9.9m compared with 2017-18.

The home secretary, Sajid Javid, used his first major speech after his appointment in May to offer an olive branch to rank-and-file officers, following years of acrimony over funding cuts and staffing reductions.

He pledged to provide “tools, the powers and the backup that you need to get the job done”. “I am listening and I get it,” he said.

A National Police Chiefs’ Council spokesman said many forces had received record numbers of emergency and non-emergency calls this summer, adding: “We are working with police and crime commissioners and the Home Office to review our demand and resources in the run-up to the next Government spending review.”