Children under 13 'able to buy knives' in London shops
Children as young as 13 bought knives in London when teenage volunteers were used to test if shops were complying with the law.
Out of 724 test purchases carried out by London Trading Standards, 96 retailers sold knives and blades to the volunteers.
It is illegal to sell knives to anyone under the age of 18.
As a result, 19 traders have been prosecuted while others received 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."
The tests were carried out as part of the Metropolitan Police's Operation Sceptre initiative, aimed at reducing knife crime.
Ch Insp of the Met's Trident Central Gangs Command, Gary Anderson, said although the force had "reduced the volume of gang-related knife crime" through education programmes and "targeted work on boroughs", more needed to be done.
"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," he said.
The government said more work needed to be done and that it would continue to work with other agencies to keep children and communities safe.
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.
"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."