Over the last 12 months there were 137 attempted test purchases in the resort – and 38 actual sales of knives to under-18s, an average of 27 per cent.

A national report by the Trading Standards Institute (TSI) – which showed the national average was 25 per cent – found 214 out of 835 stores sold knives to children with no questions asked.

It calls for more action to prevent sales of blades in shops and a blanket ban on buying knives on the internet.

The purchases in Blackpool included a variety of knives including large combat weapons, everyday kitchen knives and smaller pocket blades.

Tim Coglan, head of trading standards at Blackpool Council, said: "These figures are around the national average but we want it to be well below that.

"There are still retailers out there who feel they can get away with it.
"More than 90 per cent of youngsters in Blackpool now carry a proof of age card and all it takes it for the shopkeeper to ask for it but some of them still forget.

"The message is simple, if you sell knives to underage people you will be caught and prosecuted and be up in front of the court facing charges."

Last month a 16-year-old boy was sold a set of knives and a meat cleaver from a store on Victoria Market on Waterloo Road in South Shore. The same boy was also sold a packet of snap-off knives by a shop assistant at the Pound Express store, also on Waterloo Road.

And last year, Tesco on Clifton Retail Park, Asda on Cherry Tree Road, Glynn Web on Vicarage Lane and the Debenhams store at Houndshill all sold potentially lethal weapons to youngsters.

Supt Richard Spedding, the force co-ordinator on knife crime, said: "In Blackpool, we have concentrated not only on the larger retailers but also charity shops, discount stores and market stalls to make sure we receive an accurate picture of the situation.

"Our failures appear to be more prevalent in the discount shops and market stalls and these traders have been strongly reminded not to sell knives in any shape or form to young people."