Sir Ian said the force was doing all it could to combat violence
Every parent has a duty to find out if their child is involved in knife crime, Metropolitan Police (Met) Commissioner Sir Ian Blair has said.
Sir Ian said parents must question their children about knives in the same way they do about drugs and alcohol.
So far this year, 14 teenagers have been murdered in London, 11 of them stabbed to death.
Sir Ian said his force was using every resource to fight the rise in youth violence in the capital.
In 2007, 26 teenagers were murdered in the city.
Sir Ian said his force was "bending every sinew" and using every available resource to stem youth violence, and said parents were vital in the fight against it.
"The knives we are seeing are not nearly as often home-made constructed weapons, as weapons you would take from the kitchen drawer," he said.
"Parents have a duty now to be asking their teenagers, 'are you involved in this knife carrying'?'"
He added: "In the same way as you should be questioning your children about drugs and excessive alcohol, you should also be clear with them that carrying a knife outside the home is likely to lead to really serious trouble and tragedy."