I am sure part of it is about vulnerability for some children, some it will be about having a power over others and for others it will be about aping adult behaviour

Professor Neil McKeganey

The research team, which has published its results in the British Medical Journal, discovered children as young as 11 were regularly carrying knives.

In a survey of Scottish children, a third of boys aged between 11 and 16 said they had been in possession of an offensive weapon, compared with one in 12 of girls.

The researchers discovered those taking drugs were up to five times more likely to carry a knife or something similar.

Although the findings are clear, Professor Neil McKeganey, of Glasgow University's Centre for Drug Misuse, which carried out the research, said the result could not be properly explained.

Police have targeted people carrying knives

He explained: "I am sure part of it is about vulnerability for some children, some it will be about having a power over others and for others it will be about aping adult behaviour.

"We identified that link but other people need to carry out why that link is so strong."

Scottish National Party justice spokeswoman, Roseanna Cunningham MSP, said there should be "horror and surprise" at the shocking statistics.

"We should all be concerned about these findings. The problem with knives is that whatever the intention of carrying them might be the invariably do get used and injuries are caused.

"I think the key to improving the situation is educational," she said.

'Knives are cool'

Simon Knight, of Generation Youth, an organisation which represents Scotland's young people, said he was surprised at the reaction to the findings.

"Young people carry knives because it is cool, because it is illicit," he said.

In the past two months, Strathclyde Police have seized thousands of weapons from young people.

Officers believe the research will help them become better at targeting problem areas.

Carrying weapons is linked to drug use

Superintendent Barrie Dougall, of Strathclyde Police drugs squad said the research came as no surprise, given the knife-carrying culture in the west of Scotland.

The worrying fact was that young children were among those who had been caught with weapons, he added.

Judith Gillespie of the Scottish Parent Teacher Council said it was important not to read too much into the research, but she conceded it was worrying.

"It's obviously of concern because nobody wants any evidence of knife carrying by young people," she said.

"It's not something one wants to promote, it's something you want to stop.

'Counter knife culture'

"There's a feeling, perhaps, that knives are less dangerous than guns, but they're not less dangerous because they can still kill."

She added: "Youngsters might inadvertently use a knife thinking the consequences would not be so serious."

The report prompted a call from the Liberal Democrat's education spokesman, Jamie Stone MSP, for a new strategy to counter the "knife culture" in schools.

"I would never like to see the day where, like in America, schools are patrolled by security guards and that the entrances to schools resemble passport control with walk-through metal detectors, but clearly something has to be done," he said.

Mr Stone plans to raise the matter with the Scottish Executive.