Exclusive interview with Met Police commissioner Sir Paul Stephenson

His interview was given in the same week as Nathan Allen was shot dead in New Cross and 16-year-old Nick Pearton was stabbed to death in a Sydenham park.

Sir Paul believes the issues surrounding violence in south-east London cannot be resolved by policing alone.

He said: “I know we have an important role, but for me much of the debate stops and starts with policing, that's just not good enough.

"I largely deal with the back end of the problems we already have. These problems are of an old age. What are the real issues that force young people to choose the wrong family - the gang family rather than the family at home?

"Addressing these social problems is the key. These are jobs for the politicians at local level and the new government. I don't do social engineering, I'm a cop."

He called each murder of a young person, especially by another young person, “a tragic stain on the reputation of this city”.

Sir Paul said we needed more responsible parenting, the presence of capable role models and better police co-operation with schools - to combat social deprivation and to address issues that saw 40 per cent of young people who ended up in custody, and one in four adult offenders, coming from the care system.

He refused to accept the Met had not made progress in its fight against youth violence, as levels threaten to exceed those seen in 2008. He said Operation Blunt, the Met’s anti-knife crime campaign, had been a success, and that controversial stop and search policies were effective, with 90 per cent of all people caught with a knife charged.

And he stopped short of directly criticising the low percentage of custodial sentences handed out to people caught carrying a knife as a poor deterrent.

He said: “Recent figures show about one in five people caught with a knife go to prison, while gun possession nearly always carries a significant jail term.

“It is blatantly obvious carrying a knife against the backdrop of some of the terrible events we have seen is a serious matter. I am always keen for a serious matter to mean a serious sentence.”

He accepted there had also been too much of a shift away from sentencing and towards cautioning and fixed penalty notices for “low level thuggery” which made people feel unsafe on the streets.

He said in the summer months, when gang activity is generally considered to be at its highest, there would be more police patrols, knife arches and “disruptive tactics”.

Greater co-operation with schools to allow knife arches and other police operations to take place in them is a priority for the Met, and while he understood some schools wanted to protect their reputations by not having the arches, he said they needed to “understand their role in preventing more of these murders”.

With police funding expected to be slashed, Sir Paul said he was sure the time of growth of the police was finished and did not deny the Met now faced 10 years of austerity.

He did not rule out loss of frontline police officers but said until he knew his exact budget he would only be speculating on what would happen.

The loss of 455 officers by 2012, referred to by Boris Johnson, was mainly related to “cheaper” civilian officers being used in custody suites in police stations, he said, not frontline patrolling officers.

Sir Paul said the Met had already been looking at ways to cut costs while putting more police on the streets, including reverting to single patrolling where appropriate, which he said was the equivalent of 418 new patrols.

A massive growth in the special constabulary had also boosted town centre patrolling on Friday and Saturday nights, he said, while confirming no powers of arrest would be given to PCSOs.

Sir Paul said he understood why there had been community opposition to plans to close some police stations across south London in favour of civilian-run “police counters”, but added it was important to understand the police had a Victorian housing stock that was not right for the 21st century.

He said the police were under pressure to cut costs, and closing a fully-staffed police station that no-one visited at night would free up funds to put more officers on the beat.

But Sir Paul conceded the biggest issue in the capital is violent crime.

He said: “It is clear that the biggest concern for Londoners is safety and violence, and we are doing everything we can in this area to see a reduction. While we might have some success, we are facing challenges at the moment. We are using resources where they are needed to ensure the public feel as safe as possible and we catch those responsible for these violent crimes.

"But I understand these reassurances will be of little comfort to the families of those who have lost their loved ones to this violence, and in the communities where these crimes are occurring.

"I can only say we will do everything we can to make our streets safer and catch the individuals responsible for these violent crimes when they do occur."