Four major retailers each sold knives to under-age children at least 15 times during test purchases, National Trading Standards has claimed.

Asda, Tesco, Poundland and Home Bargains were all named as having sold knives to under-18s when the tests were carried out between April 2018 and March 2019.

Tesco and Asda have further restricted knife sales since the tests were carried out, while Poundland, which stopped selling kitchen knives in October 2018, said it was “baffled” by the figures.

Home Bargains has been approached for comment.

In total, trading standards teams carried out 2,231 tests at various national chains and independent stores over the 12 months, with shop staff failing to prevent the sale of a knife to a child on 344 occasions, equal to 15%.

Chairman of National Trading Standards Lord Toby Harris said: “Restricting the sale of knives to children is clearly a difficult issue for retailers, especially those with large numbers of outlets, staff and delivery partners, and I am aware that many retailers are working incredibly hard to train staff and introduce robust procedures to stem the flow of knives to children.

“But let’s be clear – it’s illegal to sell a knife to a child. Our tests show that it’s still too easy for a child to buy a knife.”

Figures published in April showed police in England and Wales recorded 40,829 offences involving knives or sharp objects in 2018, the highest number since comparable data started in 2010/11.

A spokesman for Asda said: “In April 2019, we became the first retailer to remove all single knives from sale across our stores to help ensure that they do not fall into the wrong hands.

“Whilst we are clearly disappointed with the results from a small number of cases between April 2018 and March 2019, we would like to reassure customers that we have since provided updated training for colleagues and have clear Challenge 25 policies in place to ensure we meet all our responsibilities as a retailer.”

Tesco said it has made a number of changes since the test purchase period. Single kitchen knives are kept in locked cabinets in larger stores and two members of staff check a customer’s age. This will be applied to all knives later this year.

No knives are sold in Express or Metro stores or on the supermarket’s website.

Tesco UK and Ireland chief executive Jason Tarry said: “Tesco takes the safety of our colleagues, customers, and the communities we serve very seriously, and we have made significant changes to our approach to displaying and selling knives, without taking choice away from customers, including a new two-stage age verification process and removing knives from display on the shop floor.”

A spokesman for Poundland said: “As this body is aware, we’re baffled by their numbers.

“They know we stopped selling kitchen knives completely in all our 850 stores last year.”

Earlier this year, the Local Government Association warned that funds for running test purchase operations were running dry.

Councils’ trading standards teams are also concerned they do not have the necessary resources to enforce a new ban on selling knives and dangerous corrosives online to under-18s.

They will have new responsibilities for undertaking under-age test purchase operations at the point of delivery for online knife sales, and for enforcing restrictions on sales of acids and other corrosives.