Knives can be purchased on Facebook Marketplace without age verification despite a recent law requiring checks, the Guardian can reveal.

In May, the UK government made it illegal to send knives sold on the internet and elsewhere to homes without ensuring the buyer was over 18 as part of reforms to strengthen existing legislation.

However, the Guardian was able to purchase four sets of knives from sellers on Facebook Marketplace without age checks. The knives were then sent to a residential address.

It is the job of councils’ local trading standards departments to enforce knife sales laws, while the onus for verifying buyers’ ages on Facebook ultimately lies with the individual sellers – often members of the public – in the absence of a regulated age-checking system.

A wide selection of culinary knives are available on the social media site, including nine-inch cleaving knives, as well as a limited number of non-culinary knives which are not allowed to be sold on the platform.

Facebook said it worked quickly to remove any such items, and invited the Guardian to highlight adverts which did not conform to its policy. It subsequently removed one item, a culinary Damascus steel chef knife which came with a free non-culinary knife.

“We take safety very seriously, which is why you have to be 18 or older to use Facebook Marketplace,” a spokesperson said. “We do not allow the sale of non-culinary knives on Marketplace and work quickly to remove these items.”

Facebook ascertains the age of its users by asking people to provide their date of birth. It recognised it could do more to ensure children could not access inappropriate content.

Patrick Green, the chief executive of the Ben Kinsella Trust, said retailers had age checks which could not be circumvented and that Facebook and its online marketplace had a legal and moral responsibility to keep knives “out of the hands” of young people.

“Without the need to employ much subterfuge to disguise their age, large knives can be purchased from this site and delivered without robust checks taking place,” he said. “Facebook not only have a moral duty to bring this site up to standard, but a legal one too.”

The Home Office said it was an offence to sell any bladed article to a person under 18 and that the Offensive Weapons Act, which passed into law in May, bans online sellers from sending knives to residential addresses unless age verification checks are in place.

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“It is totally unacceptable for social media companies to allow the illegal sale of weapons on their platforms and they must do more to stop this practice, as well as reporting it to the police,” a spokesperson said. “We are making it harder than ever for young people to purchase knives, including online.”

Although the Home Office has supported “enforcement activity” in more than 1,000 cases of physical retailers selling knives to children, it said the laws around everyday knife sales were for trading standards departments to enforce.

National Trading Standards (NTS) has urged retailers and online marketplaces to strengthen their approach to illegal weapon sales. It said that local trading standards departments were ultimately responsible for policing the sales.

“Our findings from a new programme of test purchasing has identified a number of retailers selling knives without undertaking required age verifications,” a spokesperson said.

“The programme, which is funded by the Home Office and started in October 2018, has revealed a 41% failure rate among online retailers. Enforcement action is ongoing, so we can neither name retailers who failed the checks or comment on potential enforcement measures at this time.”

The Conservative MP Ross Thomson, an officer with the all-party parliamentary group (APPG) on knife crime, called for the government and police to urgently investigate any evidence that knives were being sold illegally on Facebook.

“There is little point in passing legislation if it is not being upheld,” he said. “Facebook must be challenged on the ease with which people are able to purchase these items online.”

Recently drafted government legislation has proposed the establishment of an independent regulator to hold online companies to account over the sale of illegal goods and make them more responsible for children’s safety online.

A number of high street and online retailers have restricted access to knives in their stores, or stopped selling them altogether, as knife crime surges across the UK, particularly in London.