Nearly one in ten boys have carried or used a knife, gun or other weapon by the age of 17, double previous estimates, a major new study has revealed.

The research, by UCL’s Centre for Longitudinal Studies, found a quarter of those had also been directly involved in serious gang violence or crime.

It means more than 30,000 teenage boys may have broken the law by being in possession of a weapon, and nearly 10,000 have been directly involved in serious gang violence or crime.

Even among girls aged 17, it was one in 25 (3.9 per cent) that had carried or used a weapon. For all 17-year-olds of both sexes, it was 6.6 per cent, equivalent to more than 45,000 teenagers, and nearly double the rate of 3.7 per cent when they were aged 14.

Dr Aase Villadsen, one of the researcher, said the study also uncovered “worrying” links to “negative” childhood experiences including domestic abuse between parents, drug abuse, exclusion from school and mental health problems.

More than a third (36 per cent) of those who had carried a weapon (some 18,000 teenagers) said they had been involved in 10 or more crimes in the past year, ranging from assault to burglary and vehicle theft.

They were also 10 times more likely to have ever been a gang member compared to those who had not carried a weapon, 26 per cent versus 2.5 per cent.

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They were also 10 times more likely to have engaged in neighbourhood crime, such as breaking and entering, stealing from others, or vehicle theft (20 per cent versus 1.8 per cent)

And they were seven times more likely to have engaged in criminal damage and arson (51 per cent versus 6.8 per cent), and two and a half times more likely to have committed assault (66 per cent versus 25 per cent).

Two of the strongest determinants of involvement in knife crime was substance misuse including alcohol, smoking and drugs, and whether they had been excluded from school between the ages of 11 and 14.

Dr Villasden said: “With this research helping to pinpoint core areas for intervention in childhood and adolescence, it is imperative that investments are made in early intervention and prevention to focus on those most at risk of engaging in weapon carrying or use.