Children as young as 13 have been able to buy knives from retailers across London in tests by police and Trading Standards.

Some 96 retailers sold knives and other blades to child volunteers during 724 tests carried out by London Trading Standards.

It is illegal to sell knives to anyone under 18.

Trading Standards carried out the tests, using volunteers with an average age of 14, as part of the Metropolitan Police Operation Sceptre initiative, aimed at reducing knife crime.

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As a result, 19 traders have been prosecuted or have cases pending, while others received official warnings and compliance advice.

London Trading Standards spokesman Steve Playle said: "Whilst it is commendable that 87% of shops refused to sell, it is concerning that children as young as 13 were actually sold knives."

Chief Inspector of the Metropolitan Police's Trident Central Gangs Command, Gary Anderson, said: "Through the delivery of education programmes and targeted work on boroughs we have successfully managed to reduce the volume of gang-related knife crime.

"However, more work still needs to be done and we remain committed to working in partnership with Trading Standards to prevent knives from reaching dangerous hands and to reduce the number of families devastated by knife crime in London."

Minister for Vulnerability, Safeguarding and Countering Extremism Sarah Newton said: "Selling knives to children is illegal and I am delighted that London Trading Standards are taking action to enforce this and have found that the vast majority of retailers are complying with the law.

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"Knife crime can have devastating consequences and this Government is acting against it, including banning the sale of so-called 'zombie-knives', supporting Operation Sceptre and expanding our work with retailers to stop the underage sale of knives.

"But the results of these test purchases shows there is still more to be done and we will continue to work together to do all we can to keep our children and communities safe."