Video report by ITV News Correspondent Richard Pallot
The prime minister has been accused of being "delusional" for insisting police cuts are not to blame for a 93% rise in knife violence among young people in England.
Theresa May vowed to tackle the causes of knife crime by addressing the issues which led “so many young people” to carry blades as she rebuffed claims reductions in police numbers and cuts to youth services have contributed to the rise in violent crime.
Mrs May, a former home secretary, insisted there was “no direct correlation between certain crimes and police numbers”.
“What matters is how we ensure that police are responding to these criminal acts when they take place, that people are brought to justice,” she said.
Mrs May's statement came after two teenagers were stabbed to death at the weekend and was contradicted by Scotland Yard Deputy Assistant Commissioner Graham McNulty who indicated that extra officers did make a difference in tackling the problem.
Speaking outside Scotland Yard he said: "One incident, one injury, one death is one too many" as he addressed the past "tragic 10 days in London".
More officers from the Met's violent crime taskforce are out on patrol and their shifts are being extended amid the latest attacks, he said.
He added they have carried out 2,500 stop-and-searches in the last three days.
John Apter, national chairman of the Police Federation of England and Wales, went even further on the issue.
He said: "Our Prime Minister is delusional, steadfastly refusing to acknowledge what is plain for everyone else to see, and in the face of a national crisis that is deeply concerning."
"Policing has been stripped to the bone and the consequences are clear, splashed across newspaper front pages and TV news bulletins - children being murdered on our streets.
"What makes this all the more sickening is that it was predicted. This is the true cost of austerity that we warned of but were ridiculed for doing so," he said.
The prime minister did not expand on how the government would tackle the problem, with the home secretary Sajid Javid saying there was "no single solution" to tackling serious violence during an Urgent Question in the Commons on Monday.
Video report by ITV News National Editor Allegra Stratton
Earlier, Javid vowed to see "what more can be done" when he chairs a meeting of police chiefs on Wednesday to discuss strategies for fighting knife crime.
"Young people are being murdered across the county & it can’t go on," he tweeted.
Mr Javid told MPs: "We all wish there was one thing, just one thing, that we could do to stop this violence, but there are no shortcuts, there is no single solution.
"Tackling serious violence requires coordinated action on multiple fronts."
"We’re taking action on many fronts & I’ll be meeting police chiefs this week to hear what more can be done. Vital we unite to stop this senseless violence."
Jodie's uncle Dave Chesney condemned the "totally random and unprovoked attack" as he paid tribute to his "beautiful, lovely and quirky" niece.
His statement to ITV News came after the teenager's grandmother, Debbie Chesney, called for an end to the "needless violence". Police are appealing for help in finding two suspects.
Two 17-year-old boys were arrested after the stabbing of Yousef on Saturday evening.
The two teenagers remain in custody with police granted an extra 24 hours to question them.
The deaths came as it emerged the number of children and young people linked to murders and manslaughters using knives has risen by more than 75% over three years.
Channel 4’s Dispatches found the number of police recorded offenders aged under 18 committing homicides using a knife or sharp instrument rose by 77% from 26 to 46 from 2016 to 2018.
The analysis was based on Freedom of Information request responses from 29 out of 43 police forces about the age of offenders recorded as carrying out knife and sharp instrument offences.
It also found that during this period the number of police recorded offenders aged under 18 committing rape and sexual assault with a knife rose from 24 to 33 and robbery with a knife increased from 656 to 999.