The United Kingdom's Metropolitan Police Chief Cressida Dick has said there is "some link" between falling police numbers and a rise in violent crime a day after British Prime Minister Theresa May sparked a backlash, with her comment that there was "no direct correlation between certain crimes and police numbers".

The response comes after two 17-year-olds were killed in separate stabbings in London and Greater Manchester at the weekend, and amid new evidence of a significant rise in teens using knives.

"What matters is that police are responding to these criminal acts when they take place, that people are brought to justice, but what also matters is as a government we look at the issues that underpin this use of knives and that we act on those," said May, who promised "a cross-government response".

But a political row erupted over the government's grip on knife crime as police and crime commissioners, senior officers, and youth workers pushed back against May's comments.

Labour leader Jeremy Corbyn said May "must start listening" to police chiefs over the impact of cutting 21,000 officers, adding: "You cannot keep people safe on the cheap." Labour called the rising death toll from stabbings a national tragedy and attacked what it claimed was a lack of leadership by May.

The UK home secretary, Sajid Javid, later defended the government's record and told the Commons that knife crime was "a huge priority across government". Javid is set to meet police chiefs on Wednesday to discuss the problem.

"I really wish standing here there was just one simple answer, one single thing that could be done," Javid told MPs. "We require action across multiple fronts and the best way to achieve that is for all of us to recognize that and to work together to deliver it."

New police figures released on Monday showed a 53 percent increase in the number of teens using knives for robberies, murders and rapes or sexual assaults between 2016 and 2018. The number of children under 16 being treated for blade wounds almost doubled in the last five years, NHS data has shown.

Speaking about policing numbers, Met police chief Dick said: "If you went back in history, you would see examples of when police officer numbers have gone down and crime has not necessarily risen at the same rate and in the same way.

"But I think that what we all agree on is that in the last few years police officer numbers have gone down a lot, there's been a lot of other cuts in public services, there has been more demand for policing, and therefore there must be something, and I have consistently said that.

"I agree that there is some link between violent crime on the streets, obviously, and police numbers, of course there is, and everybody would see that."

Dick also agreed that middle-class recreational drug users had "blood on their hands" over recent deaths, adding the drugs trade was a key driver behind street violence.