One in two online retailers are willing to sell a knife to a child with no checks, a police investigation found.
A ‘hard core’ of high street retailers, often small independent shops, are also failing to observe the law, senior officers said.
They called for tougher measures to stop deadly weapons getting into the hands of under-18s as they battle a surge in offences.
Police want tougher measures to stop children from accessing deadly knives, file photo
Crimes involving knives have soared by a fifth, with worrying increases in robberies and sex attacks involving blades.
Police fear street gang members think they can get away with carrying weapons thanks to the controversy around stop and search operations.
The Government called for the number of people stopped in the street to be cut dramatically as ethnic minorities were being disproportionally targeted.
Thousands of officers will join a nationwide crackdown next week aimed at driving knife-wielding criminals off the streets.
Deputy Assistant Commissioner Duncan Ball, who is leading the drive, said it is still ‘too easy’ for underage customers to get knives via the internet.
Police fear young people find it too easy to access potentially deadly knives, file photo
The Metropolitan Police officer said he was surprised when a 15-year-old working alongside police was able to buy a knife online every other attempt.
He suggested it was unacceptable for retailers to deliver knives to addresses without checking the age of the recipient, or even just leave parcels outside.
‘We know it is still easy for young people in particular to get hold of knives from online retailers,’ he added.
‘A proposal where a knife has to be collected at a certain pick up point with ID is a strong one, rather than it just being delivered to an address where to can be picked up by anyone.’
Last year there was a 21% surge in recorded crimes involving a knife, including a 13% rise in murders, 44% rise in sexual assaults and 28% rise in rapes.
Only six of the 44 forces in England, Wales and Northern Ireland did not see an increase in knife crime. In five forces crimes soared by half.
Police are desperate to stem the rise, which is particularly acute in major cities, particularly as many victims are teenagers.
They want retailers, both online and in the high street, to do their bit to keep knives away from violent criminals.
Major stores, including supermarkets and DIY chains, have all signed a voluntary agreement to challenge anyone who appears under 21.
Amazon has pledged to check the age of customers at the point of delivery and eBay has banned the sale of all knives except cutlery.
But Mr Ball said in some cases people ordered so-called ‘zombie knives’ from foreign websites to be delivered with no checks.
The fearsome weapons, which have become cult items as a result of horror movies and computer games, cannot be sold in the UK.
He said that a small number of high street shops, mostly independently owned, also continue to sell knives illegally.
‘We have seen importation of knives ordered from overseas, where they come and are delivered to young people’s address,’ he said. ‘That availability is a concern.
‘If you can introduce that point where somebody is asking for identification when you are picking it up, whether it’s a row of kitchen knives or whatever, that is one additional safeguard.’
Last year the Home Office revealed plans to make it an offence to deliver a knife sold online to a private residential address.
The buyer would have to collect the knife in person at a location where their age can be checked.
Speaking about the controversy around stop and search, Mr Ball said it has left some street criminals feeling more confident about carrying weapons.
‘What we hear back from our officers who speak to gang members for example, they consider they will be searched less,’ he said.
‘Because of the coverage that issue has had, bearing in mind the stop and search journey, I think from that perspective there is less fear they will be searched.
‘One of the things we are doing in London and what we are pushing for is intelligent use of stop and search, and not increased use of stop and search for the sake of it.’
The nationwide crackdown, known as Operation Sceptre, will see extra police at knife crime hotspots and transport hubs, undercover knife purchasing and weapons searches in parks and on estates.