Labour's war on teenage offenders has failed to cut crime despite public spending rising by 45% in real terms, according to an authoritative new study.

The research, to be published this week, shows that new laws, high-profile initiatives and nearly £3 billion spent by government and police agencies have “had no measurable impact” on the level of youth crime. It shows that a quarter of young people still admit to having committed a crime in the previous year — a figure that has not changed since Labour came to power in 1997.

The study — by the Centre for Crime and Justice Studies (CCJS) at King’s College London — will undermine efforts by Gordon Brown to dispel growing public disquiet over the scale of violent crime and anti-social thuggery by young offenders.

It also dismisses as misleading and exaggerated claims by ministers that Labour has reduced the problem. “Despite substantial investment in radically restructuring and expanding the youth justice system, success has been far more mixed and ambiguous than the government says and claims of significant success are overstated,” the study maintains.

The report says annual spending on youth justice in England and Wales has risen to record levels, from £381m in 2000 to £648m last year — a total of £2.9 billion over seven years.

But citing the most recent figures from the Mori Youth Survey, a poll of 11 to 16-year-olds, it says 27% of schoolchildren admitted in 2005 to having committed an offence in the previous year. This compares with a consistent 26% in 2002, 2003 and 2004.

This weekend David Davis, the shadow home secretary, said the findings showed the government did not know what it was doing when it came to violent crime.

“Three billion pounds is a hell of a lot of money to have been spent to produce absolutely no result,” he said.

“This underpins the fact that ministers are failing totally to get a grip on violent crime. Look, for example, at London, where we have had 100 stabbings this year. It’s a demonstration that the government doesn’t really understand the problem and therefore can’t solve it.”

Cases such as the murders last summer of 11-year-old schoolboy Rhys Jones in Liverpool and Gary Newlove, 47, from Warrington, Cheshire, who was kicked so hard after confronting a gang that he died two days later, have triggered a wave of concern over teenage crime.

Last weekend, Jimmy Mizen, 16, was murdered when his throat was slashed with a shard of glass at a south London bakery.

There have been 39 teenage murders in London alone since January last year.

The growth in gang-related knife and gun crime has prompted Brown and Jacqui Smith, the home secretary, to chair a series of Downing Street summits to tackle the problem.

Those moves, however, have failed to quell the growth in youth violence. Figures produced by the Youth Justice Board (YJB) last week show that cases of violence by young people, ranging from common assault to murder, are up 39% over three years. Some 56,000 violent incidents involving teenagers were recorded in 2006-2007, up from 40,000 in 2003-2004.

The new report is the first of its kind to compare the amount of public money spent by ministers with its impact on crime.

Figures for crime among young people are notoriously difficult to obtain. Those younger than 16 years old are not included in the British Crime Survey, the government’s preferred method of measuring the level of offending.

The new study uses confidential interviews with thousands of young people about their involvement in crime.

“It is striking to note that there is no indication that the creation of the YJB, youth offender teams and the greater focus on youth offending . . . had an impact on reducing self-reported youth offending levels,” it says.

The study highlights Labour’s shift to a more punitive approach to youth crime since it came to power more than a decade ago.

But the CCJS study suggests this move — which helped Labour to win over many disillusioned Tory voters in 1997 — may have been been misjudged.

It suggests that instead of the lion’s share of public money being spent on prison places for young criminals, more should be spent on early intervention and a “welfare approach”.

The slow death of Labour’s so-called “respect” agenda is said by critics to signal the demise of the hardline approach. New figures out last week show that the use of antisocial behaviour orders (Asbos) to stop yobbish behaviour has failed to tackle teen offending. The number of new Asbos issued has declined by 34%. The proportion breached by teenagers, meanwhile, has soared to 61%.

Whitehall insiders say that with a record prison population of more than 82,000 and full jails, fresh questions are being raised about the viability of long prison sentences. The rift between the two approaches was highlighted last month when reports emerged of a turf war over youth justice between Jack Straw, the justice secretary who favours a “softer” approach to youth crime, and Ed Balls, the more hardline schools secretary.

Richard Garside, director of the CCJS and one of the report’s authors, said: “Labour’s youth justice reforms were a bold experiment. Our research suggests that they have largely failed in the key objective of tackling and reducing youth crime. The government’s record on addressing the multiple needs of children caught up in the youth justice system is also less impressive than many would have expected, given all the money that has been spent.”

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