The Mayor of London also called on government ministers to "stop shirking their responsibility" after government cuts to local authority budgets since 2011 have led to £22 million less being spent in London on youth services.
The cuts have meant 30 youth centres, serving around 12,700 young people, have been lost since the Conservative government came into power.
Schools in London also face a funding gap of around £99 million this year, while children's services are facing an estimated funding gap of £2 billion by 2020.
Mr Khan, said: “The Met will do everything in their power to tackle violent crime, which is rising across the UK, but this Government has forgotten that there are two parts to this equation.
"The police are being tough on crime, but the Government are being desperately weak on the causes of crime."
During New Year festivities, unrelated stabbings in north, east and south London claimed the lives of a 17-year-old boy, an 18-year-old and two 20-year-old men.
Met officers arrested more than 900 people and took more than 350 weapons off the streets in Operation Winter Nights which ran from November to December 2017.
However, violent assaults went up 3% in the last year alone in the capital and more and more young people are going on to reoffend.
Latest figures show 38.9% of males aged 18 to 20 are re-offending after prison sentences.
“Getting back to being ‘tough on the causes of crime’ will require a massive investment in the services that have been neglected for too long, tragically letting our young people down," added the mayor.
“Ministers need urgently to prioritise local services, youth services, early years, community work, mental health services, probation and prisons if we are to bear down on the senseless violence in which four young men lost their lives this new year."
He added: "On this government's watch, these critical services have been allowed to deteriorate and starved of funding and we are now paying a heavy price.
“Keeping Londoners safe is my priority, and I am doing everything I can to tackle this scourge in our communities.
"Keeping the country safe should be the government’s priority too, and it is time ministers stopped shirking this responsibility.”
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