Sir Keir Starmer vowed to close legal loopholes that tech giants use to sell dangerous weapons to criminals.
Setting out his “mission” to slash crime if he gets the keys to No10, the party leader said it was outrageous that they can still be bought on Amazon and eBay.
Speaking to The Sun ahead of a major crime speech on Thursday, he said “online criminals have run rings round” the system.
Sir Keir said: “Big tech companies maintain a small army of lawyers and lobbyists with one aim: to protect their own interests, often at the expense of others.
“We can’t hope to tackle crime without getting serious about this.”
The Offensive Weapons Act 2019 banned the sale of knives to under-18s and made specific blades such as machetes and zombie knives illegal.
But Labour say a loophole means online marketplaces are not bound by it.
Labour would introduce criminal sanctions for online executives as part of the Online Safety Bill.