The number of teenage murders in London will reach a record level this year as police struggle to cope with the surge in youth and gang violence.

The toll reached 26 with the death of Oliver Kingonzila, 19, at the weekend – the same as the total for the whole of 2007, with three months of 2008 remaining.

Scotland Yard said yesterday that youth violence was its “biggest challenge”, while senior detectives privately conceded that further deaths were almost inevitable.

Sir Ian Blair, the Metropolitan Police Commissioner, described the youth murders last year as “completely unacceptable”. But tough enforcement measures, a high detection rate and millions of pounds being spent on antiknife crime initiatives have not stopped the rate of killing rising sharply from 17 in 2006, 16 each in 2005 and 2004, and 15 in 2003.

There are also signs of the teenage gang culture spreading to other parts of the country. In Sheffield, a city of 500,000 people, there have been three teenage murders in the past year.

What makes the Met’s problem more frustrating is that the level of teenage deaths is overshadowing its overall success. The number of homicides in the capital has fallen from 222 in 2003 to 160 last year.

Mr Kingonzila, 19, was a semi-professional footballer with Barnet FC who once captained the English Colleges FA team against Italy. The teenager, whose 27-year-old brother died from a heart attack six months ago, was stabbed during a fight outside a nightclub in Croydon in the early hours of Saturday.

Friends said that he had been the victim of an unprovoked attack. His mother, Caroline, said: “Oliver was a kind and gentle boy. He never carried a knife and could never harm anyone. I don’t know why he was attacked. I am devastated.” Two suspects, both aged 18, were arrested, one of whom was later bailed.

So far this year the victims, both boys and girls, range in age from 14 to 19. Twenty-one have been stabbed, three shot and two died from head injuries. The death of another teenager, who died when he fell from a tower block while being chased by a gang, is not being treated as a murder.

At the beginning of the year Sir Ian said that only terrorism posed more of a threat than youth violence. But two months ago his deputy, Sir Paul Stephenson, said that knife crime was now the Yard’s number one priority.

Operation Blunt 2, a high-profile initiative to tackle knife crime, was launched involving the use of airport-style metal detectors, search wands and emergency stop-and-search powers. Since it began 35,000 people have been searched and 1,900 knives seized.

Speaking before Mr Kingonzila’s death, Commander Mark Simmons, who is leading the operation, told The Times that police could not solve the problem alone. He said: “Schools, referral units, youth offending teams, local authorities and youth services all have a role to play. Some say it comes back to early-years parenting.”

Mr Simmons added: “If people think it is cool to belong to a gang, remember that they will not visit you when you are in prison if you have stabbed someone, and they will not help you if you are lying on a street corner bleeding from a knife wound.”

Gloria Laycock, director of the Jill Dando Crime Institute, blamed the rise of violence partly on hype. “Kids are very susceptible to fashion,” she said. “If you get it into their heads that everyone is carrying a knife, then they will carry knives.”

Times Recommends

• Alex Rider exclusive: Incident in Nice
• Green & confused: do energy-saving bulbs work?
• Let’s skip lunch, say the hungry generation