Police leaders have written to the two Conservative leadership candidates to say whichever of them becomes prime minister should make providing more money to police and youth services their first priority.

The letter from 10 Labour police and crime commissioners overseeing the four biggest forces, and others across England and Wales, was sent to Boris Johnson, who has said he wants to hire an extra 20,000 police officers, and Jeremy Hunt, who has said policing cuts have gone too far.

Since 2010, police funding and officer numbers have fallen under the Conservatives, while provision of youth services has dramatically declined.

In the letter, the police leaders say: “Violent crime has been rising across the country since 2014 after years of spending cuts. Across the country, these cuts have affected police numbers, as well as preventative services including youth services, local councils, mental health services and schools.

“That’s why it’s encouraging to hear both the Conservative candidates to be the next prime minister accept the link between this government’s reductions in police numbers and rising crime levels, and admit that the cuts made by your government have gone too far.”

A National Audit Office report in September 2018 said there had been a 19% drop in police funding since the Conservatives took power in a coalition government in 2010, and officers were struggling to maintain an effective service.

The number of police officers and civilian staff has fallen from 244,497 in 2010 to 199,752, though the government says police are to receive an extra £970m in funding this year, a significant proportion of this from council tax.

Because cuts fell hardest on poorer urban areas, bigger forces lost the most resources. In the letter, the police leaders stress the need for immediate action from the next prime minister.

“Given it takes around nine months to fill a police vacancy, it is crucial that the funding is available as soon as possible, as any delay results in delays to recruitment and ultimately to communities waiting longer to see the benefits of additional policing,” they write.

The letter says the next prime minister needs to back up government commitments to a public health approach to tackling violent crime with new resources.

“While you have made pledges to invest in more policing, there has been no focus on addressing the root causes of crime. Cuts to youth services, local authority budgets, school budgets and mental health services have contributed to a worsening of inequality and poverty, and made efforts to prevent crime even more difficult,” the police leaders write.

“That’s why we are asking you to commit to making this your first priority as prime minister and reverse the cuts made to policing and preventative services.”

Their call is backed by the London mayor, Sadiq Khan, the police and crime commissioners for the West Midlands and West Yorkshire respectively, David Jamieson and Mark Burns-Williamson, as well as Beverley Hughes, the Greater Manchester deputy mayor for policing, along with PCCs for six other areas.