The number of children and young people who have used knives to kill has risen by more than 75 per cent over three years, an investigation has indicated.

There were 26 under-18s who committed homicides using a knife or sharp instrument in 2016 – rising to 46 in 2018, Channel 4’s Dispatches found.

The analysis was based on responses to Freedom of Information requests from 29 out of 43 police forces.

During this period, the number of under-18s committing rape and sexual assault with a knife rose from 24 to 33. Robbery with a knife increased from 656 to 999.

Dispatches also found there was a 93 per cent rise in the number of children aged 16 and under being treated for stab wounds in England.

An analysis of NHS Digital data by the programme found the number of children aged 16 and under being treated for assaults by sharp objects rose from 180 to 347 between 2012-13 and 2017-18.

The research showed that 76 people were reportedly stabbed to death in the capital out of 306 across the UK as a whole last year, including 23 children.

The programme, Britain’s Knife Crisis: Young, Armed And Dangerous, is fronted by former Metropolitan Police Commissioner Bernard Hogan-Howe and aired on Monday.

Lord Hogan-Howe, who retired in 2017, said: “One of the big challenges underpinning is the reality that for too many young people, particularly in our big cities, carrying a knife now feels normal.”

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He called for the appointment of a new “knife crime tsar” to “get a grip on the crisis”.

He said: “It’s important to focus attention on the exploitation of children in socially deprived areas.

“We need to increase police numbers in these areas and reduce the drug supply into the UK and its distribution including by county lines – something law enforcement and government have failed to do.

“I just don’t see anybody getting a grip of this crisis. The government needs to appoint somebody who is going to lead it day after day.

“Call it a ‘knife crime tsar’ if you like, but somebody who is going to make sure we get knives off the street and save lives.”

Lord Hogan-Howe also called for increased interception of Class A drugs and police numbers to rise to 20,000. He also recommended a focus on technology and building trust in local communities to reduce knife crime.

Policing minister Nick Hurd told the programme an extra £460m was being invested in the police system this year, which will be used to recruit at least 2,500 more officers.

He added: “This is a massive challenge for our policing system and therefore a big priority for me as policing minister to make sure that our police system has the resources to invest in upgrading our technology.

“One of the big challenges underpinning is the reality that for too many young people, particularly in our big cities, carrying a knife now feels normal.”

The show also used undercover filming to capture a 17-year-old girl being allowed to buy the knives in Asda and B&M without being challenged on her age or asked for ID.

It is illegal to sell a knife with a blade longer than three inches to anyone under 18 but experts say girls are used by gangs to buy them, the programme said.

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B&M, which was fined £480,000 in September last year for selling knives to under-age children, told Dispatches it takes “every precaution to prevent the sale of knives to under-age shoppers”.

The company said the checkout worker filmed by the show had received training in the previous 12 months and had therefore been suspended pending disciplinary action and further training.

It added: “We have had 104 test purchases in the last 12 months by Trading Standards for age-restricted products, with a 100% pass rate.”

Asda told Dispatches it took its “responsibility as a retailer very seriously”, had “strict processes” around knife sales and regularly trained staff on its policy.

It added: “On this occasion we got it wrong and have conducted a full investigation into what happened.”