Google is profiting from ads offering lethal weapons for sale to people in the UK – including 17in zombie knives, “military tactical” blades and “zombie killer sword apocalypse machetes” – despite claiming to ban them.

Since 2015, the tech giant has prohibited the advertising of dangerous products that carry a risk of causing “serious and immediate harm”. This includes any knives that are “designed or promoted as products that can be used to injure an opponent in sport, self-defence or combat”.

But an Observer analysis has found that, amid high levels of knife crime in the UK, the company has been violating its own rules as sponsored listings for “zombie knives” appear at the top of search results.

During recent testing, ads for zombie knives were being recommended to people searching terms such as “zombie knife UK” and “zombie knife for sale”. The ads were promoted by Google even when the SafeSearch setting, designed to hide harmful content from under-18s, was switched on.

Zombie knives, which can be up to 30in long and often have holes, multiple spikes or a serrated edge, have repeatedly been linked to violent crime. In September, a 15-year-old girl was reportedly killed on her way to school in London with a foot-long, serrated zombie blade. In the year to March 2022 there were 282 murders overall involving a knife or sharp instrument in England and Wales, the highest figure since 1946. Of those killed, 99 were under 25.

Since April, companies found to be selling knives to children have faced fines of up to £1m, proportionate to the size of their annual turnover. But last week, the weapons were available to buy via Google in a couple of clicks, without the need to provide age verification, ID, or go through vetting checks. Customers were directed to online marketplaces, mostly overseas, which offer to ship the knives to customers in the UK for as little as £20.

The promotions were condemned as “irresponsible and reprehensible” by the Victims’ Commissioner for England and Wales, Baroness Helen Newlove, who said it was “obscene” for Google to have profited from them. “Knife crime is a scourge on our society and these zombie knives recklessly glamorise and fuel a senseless cycle of violence in our communities,” she said.

“Google’s promotion of these weapons is both irresponsible and reprehensible – it is obscene to profit off human misery in this way. Recent government commitments to ban the sale and use of zombie blades and machetes are welcome but also long overdue.”

The search giant said it had now removed violating listings and had “strict policies” to keep people safe. It did not say how the ads had come to be on its platform in the first place.

The findings come amid criticism of the government for failing to act quickly enough to strengthen laws on the sale and possession of zombie knives. In 2019, the Offensive Weapons Act made it illegal to possess, sell, import or manufacture the knives, defined at the time as blades which have a cutting edge, a serrated edge and include images or words that glamorise violence.

Since then there has been criticism from charities and campaigners that weapons were still being manufactured and sold, simply with the images or words removed. In parliament in November, Yvette Cooper, the shadow home secretary, warned that a “loophole” was allowing them to be easily bought and sold via online marketplaces.

In August 2023, No 10 announced a further crackdown, unveiling plans to close the loophole by banning more of the weapons and giving police more powers to seize and destroy them. However, it is not clear when the new law will come into force. The government has said the measures “will be legislated when parliament allows”, but has not provided a timeline.

Last month, the London mayor, Sadiq Khan, accused the government of dragging its feet. “Since 2016 we’ve repeatedly been promised action on zombie knives by this government. They need to stop simply making announcements and get on with changing the law,” he said.

The weapons promoted by Google include some that appear to fit the current definition of banned zombie knives, meaning their importation and sale to the UK may be illegal.

In one case, Google accepted around 2,000 adverts from an UAE-based online marketplace, whose showcased products include a knife emblazoned with the words “Release the hounds of hell”. Others are unlikely to be banned because they did not have images or words on their blades, or because they had blades shorter than 8in.

In another case, Google accepted around 3,500 adverts from a seller whose products include a knife that is shorter than the 8-inch definition of a zombie knife yet has “zombie killer” etched on its blade.

Anti-knife crime charities have criticised Google for failing to prevent the sale of the knives despite its own policies appearing to ban them.

Patrick Green, chief executive of the Ben Kinsella Trust, said it was unacceptable that they were so “readily available online”.“These types of weapons are designed to inflict maximum damage and are being increasingly used in violent attacks on our street,” he said. He said: “While we wait for the government to fulfil its promise to ban these weapons, Google and other online retailers need to do more to prevent their sale.”

The Home Office said it was tightening the law on zombie knives, including making sentencing “more severe”, to ensure “offenders face the punishments they deserve”.

Under the new Online Safety Act, companies such as Google will have a legal duty to prevent illegal activity – including weapon sales.