Some shops in London are still selling knives and alcohol to children as young as 13 – despite it being illegal to sell knives, alcohol and tobacco to anyone aged under 18.

London Trading Standards (LTS) said that out of 2,593 test purchases over the past 18 months, child volunteers aged between 12 and 17 were sold knives, alcohol or tobacco 285 times.

The spot checks were carried out by 26 local authorities and in total 14 percent of the sales were of knives and 12 percent were of alcohol, according to the figures which have been released as part of London Trading Standards Week.

The campaign week, which runs through to September 14, seeks to raise awareness of consumer protection issues.

LTS said that a majority of shops refused to sell to underage customers.

Trish Burls of LTS said: "We are disappointed that a 13-year-old has been allowed to buy a knife in a London shop but we note the relatively high levels of compliance among the majority of retailers."

She urged retailers to continue to sign up to Responsible Retailer Schemes and said that information about shops making such illegal sales could be reported to LTS.

Sophie Linden, Deputy Mayor for Policing and Crime, said that pushing the courts to review sentences given to retailers who fail to comply with the law was among the efforts being used to try and crack down on traders who illegally sell knives.

Metropolitan Police Detective Superintendent Sean Yates said: "Knife crime devastates families and communities.

"Tackling knife and gang crime is one of the Met's top priorities, and we are working closely with Trading Standards, the Mayor's Office for Policing and Crime and retailers to do everything we can to prevent young people getting hold of knives in the first place.

"We are also targeting those who carry weapons and cracking down on online videos that glamorise and encourage this terrible violence.

"Everyone has a part to play in ending the deeply concerning rise in knife crime that we have seen across the capital and to spread the message that carrying a knife is more likely to ruin your life than save it."