Bosses at Amazon Marketplace, eBay and Instagram could face criminal sanctions for allowing the sale of illegal knives on their online platforms under Labour proposals.
The Opposition party will urge the Government to close the “glaring loopholes” in its plans to tackle knife crime.
Ministers are introducing new laws to outlaw zombie-style weapons, with the ban due to come into force in September – making it illegal to possess, sell, manufacture or transport the blades.
But Labour will use an Opposition Day debate on Tuesday to call on the Government to go further by including ninja swords in the ban and making tech executives liable for illegal weapons sold on their online marketplaces.
Sir Keir Starmer has promised to close loopholes and end caveats in a “total crackdown” on the availability of knives on UK streets.
The Labour leader last month met the family of Ronan Kanda, a 16-year-old who was killed by two 17-year-olds in 2022 using a ninja sword bought online using a fake name and collected from a Post Office.
The former director of public prosecutions pledged to conduct a review of online knife sales to strengthen ID requirements and checks on parcels by Royal Mail and Border Force in an effort to clamp down on the unlawful supply of dangerous weapons to under-18s.
A Labour government would also launch a £100 million programme aimed at identifying and supporting young people at risk of being drawn into violent crime.
Any young person caught with a knife could also face curfews, tagging or other sanctions.
Labour is calling on Tory MPs to back these proposals in the House of Commons on Tuesday.
Shadow policing minister Alex Norris said: “Knife crime destroys lives and leaves families and communities reeling.
“The Government has a duty to do everything it can to stop these dangerous weapons getting into the hands of teenagers and those who would do harm.
“Dangerous weapons like ninja swords which have been used to kill teenagers like Ronan Kanda are still available on Britain’s streets. Still, law-breaking online platforms who profit from these illegal sales are being let off with a slap on the wrist instead of facing criminal sanctions.
“Labour wants to close these glaring loopholes in the Government’s plans and are asking the Conservatives and other parties to vote with us to do so.”
A Home Office spokesman said: “The UK has some of the strongest anti-knife laws in the world, and since 2019 we have taken 120,000 knives off our streets, but we are determined to do more to end this senseless violence.
“Just weeks ago, we banned zombie-style knives and machetes and we will not hesitate to take further action based on the advice of police chiefs and frontline officers.
“We are also toughening sentences for anyone caught with a banned weapon or found selling knives to under-18s, and are giving police new powers to seize any knife if they believe it might be used in criminality.”