One of England’s most senior police officers has called for emergency funding and the convening of a Cobra meeting in Whitehall to help tackle the rise in violent crime.

Speaking before talks with the home secretary, Sajid Javid, the chairwoman of the National Police Chiefs’ Council, Sara Thornton, said the recent spate of deadly stabbings involving young people should be treated as a national emergency.

“When you have an emergency, you get all the key people around the table to solve the problem, setting up Cobra with a senior minister holding people to account, because it is not just about policing, it’s about all the other agencies and organisation. It’s an emergency and it needs some emergency funding,” she told BBC Breakfast on Wednesday.

The mayor of London, Sadiq Khan, backed the idea. In a letter to the prime minister, he said convening Cobra was necessary to “urgently improve cross-government efforts to tackle violent crime”.

Speaking later to BBC Radio 4’s Today programme, Thornton stepped up her criticism of ministers. “We think we need much stronger leadership from government,” she said. “The difficulty is that it is not being properly funded and it doesn’t appear that anybody is really being held to account for that broad strategy.”

Thornton, a former chief constable of Thames Valley police, said there was no doubt the rise in violence was linked to cuts in police numbers, despite Theresa May’s claims to the contrary.

“Just look at the facts. There are fewer police officers doing less policing and there is more crime. We know that we are taking longer to get to emergencies, we are arresting fewer people, we are charging fewer people, so I think there is a link and we need to really look at what we can do in terms of policing to stop the violence and the killings now,” she told BBC Breakfast.

“We need to have more officer hours on the streets. We know what tactics work about targeting hotspots, about using stop and search, about tackling county lines gangs, but we just haven’t got the capacity. We just haven’t got the officers at the moment, so we need some money now to pay for overtime, to pay for mutual aid between forces.”

Alongside emergency cash, Thornton called for longer-term investment to reverse cuts in police funding that have led to a 21,000 reduction in officer numbers since 2010.

“We also need to think about the longer-term investment that we are willing to make into policing. The money this year is welcome, but there needs to be serious investment in the next spending review into police,” she said.

Later on Today, Thornton suggested rising knife crime was also linked to cuts in school budgets. “We have seen, in a lot of our cities, a lot of young people roaming the streets during the day, who are vulnerable to recruitment,” she said.

“The number of exclusions has been going up; apparently it’s an average of 40 children a day who are excluded from school … And we also have higher levels of truancy, which because of cuts are going unchallenged.”

Javid supports police calls for extra cash, but has been rebuffed by the chancellor, Philip Hammond, and is thought to have clashed with May on the issue.

In an article in the Daily Mail, the former foreign secretary Boris Johnson called on police forces to “vigorously” step up stop and search operations and ignore those who claim the tactic is discriminatory.

Thornton said she would demand government coordination as well as cash at her meeting with Javid on Wednesday.

“We will be speaking to the home secretary about the case for more investment in policing, but also a senior minister getting the key departments and agencies round the table and saying what are you doing,” she said.

“There was a really good serious violent crime strategy published last year. The plans are great for early intervention, for tackling county lines, as well as more policing, but we really need somebody to be holding departments to account to make sure this is all happening.

“It’s about local officers building relationships with local communities that will make a difference, but the difficulty that we have is that we just haven’t got the capacity; we haven’t got the numbers to do that in the way we’d like to.”