A number of young men have died in the past two months

Speaking at the monthly meeting of the Metropolitan Police Authority (MPA) Sir Ian described the situation as a "cloud on the horizon".

His comments follow a series of fatal shootings and stabbings of teenagers in London during the past two months.

Scotland Yard have identified 169 gangs with about 5,000 members in London.

Sir Ian warned against adding to the "allure" of gang culture by overstating its importance.

My fear is that there is a generation who almost believe that to be a victim of crime is a rite of passage Richard Barnes, Conservative London Assembly member

"It is a cloud towards the horizon that is coming," he said. "Unless we do something about it, it will get very difficult."

He said most of the victims of gang violence knew their perpetrators, but many feared the consequences of speaking out and therefore were reluctant to go to the police .

"What we have to find is a way of encouraging these young people to trust the authorities to protect them," Sir Ian said.

He said that recent high profile cases did have an impact on how children viewed "their own safety".

Teenage stabbings

Richard Barnes, a Conservative London Assembly member, added to Sir Ian's comments at the meeting.

He said: "My fear is that there is a generation who almost believe that to be a victim of crime is a rite of passage."

Cindy Butts, a member of the Home Secretary's gun crime round table, added: "The way young people see it, it is safer and easier to be in (a gang) than to be out."

Recent teenage victims in London include Kodjo Yenga and Adam Regis who were stabbed to death.

Three other young men, James Andre Smartt Ford, Michael Dosunmu and Billy Cox, were all shot dead in February.