A terrifying new class of knife widely available on the internet from UK retailers and increasingly carried by gangs on the streets of Britain’s cities is set to be banned from sale, The Independent can reveal.

Sales of so-called “zombie killer” knives, serrated weapons with long blades inspired by horror films, have led to calls for a crackdown on the marketing methods of online vendors who sell them as collectors’ items to “exterminate the undead”.

But police forces have become so concerned at the potential proliferation of the knives in big cities that steps are now being taken to introduce an outright ban on the weapons.

Scotland Yard has warned that the knives, which can be bought for as little £8 and reach up to 2ft in length, are being used by teenage gang members to pose in online videos designed to provoke rivals.

A 24-inch curved and serrated machete, advertised as an “apocalypse head decapitator”, was recovered from an east London alleyway last year as the number of teenagers murdered with knives in the capital reached a seven-year high. The rise to 15 in the number of killings - the highest since 2008, when there were 23 deaths - has caused concern that teenagers are increasingly carrying knives in the mistaken belief they offer protection.

The Independent understands that a decision was taken at a meeting last month of police chiefs and Home Office officials to move to outlaw the zombie killer-style weapons amid fears that gang members are acquiring them as status symbols. The authorities say that they believe sales of the weaponry remain relatively low but they want to act before they become more common on the streets.

Senior officers are particularly concerned at the damage that such weapons can cause if used in an attack, warning that the mixture of sharp points and bladed and serrated edges on the knives would be likely to inflict lethal injuries in a stabbing.

Alf Hitchcock, chief constable of the Ministry of Defence Police and lead on knife crime for the National Police Chiefs’ Council, said: “These are absolutely horrific weapons for which there can be no legitimate use. You only have to look at the combination of the pointed and serrated edges to see that any injury would be fatal. The serrations would cause such serious internal damage to anyone that it would be fatal.

“Whilst we haven’t got significant evidence of a huge increase in sales, there is enough evidence for it to be worrying and we are looking to work on a form of words that bans these weapons.”

It is possible under secondary legislation to outlaw specific types of knife and other weaponry. Bans are already in place on the sale of at least 13 different types of blade, including flick knives, sword sticks and several classes of weapon associated with martial arts.

The move to ban “zombie killer” weaponry was last night welcomed by campaigners who have raised alarm at the widespread availability of the knives on UK-based websites and the manner in which they are being marketed.

Caroline Pidgeon, Liberal Democrat leader in the London Assembly, said: “Despite all the rhetoric by so many Westminster politicians about being tough on knife crime, the reality is that many practical policies have for too long not been properly adopted to tackle the horrendous loss of young lives caused by knife crime.

“The sale of so called zombie and long-bladed knives has no practical purpose other than the pursuit of violence. A complete prohibition on their sale could not come sooner.”

A Bedfordshire-based online retailer last month admitted to breaching legislation dating back nearly 20 years which makes it illegal to sell knives in a way that suggests they might be suitable for combat or “stimulate violent behaviour”.

The investigation by Bedfordshire Police, which led to the owner of the Blade Bargains site accepting a caution, is believed to have been the first time that the section of the 1997 Knives Act has been used since it was introduced 19 years ago.

Police chiefs are now keen for it to be used more widely to counter dog whistle-style marketing of weaponry to be used on the “undead” which in reality poses a potentially lethal threat to the living.

The “zombie killer” weapons first grew popular in America, where they are popular with so-called “preppers” preparing for a Hollywood-inspired fantasy invasion of ghouls.

Under current legislation it is legal sell the weapons in Britain and keep them in a private residence but they cannot be legally carried in public.

The Independent last week found at least six UK-based websites marketing the weapons.

One site, selling knives called “The Exterminator” or “The Head Splitter”, repeatedly described them as a “close up way of exterminating the walking dead”. Another site offered a 17-inch curved machete which it sells with a sheath to allow owners to have it “on the go” in potential breach of the law on carrying knives.

Mr Hitchcock said: “There are grounds for concern about the manner in which some of these knives are being marketed and I think we should be looking at further use of the 1997 act.

“The nature of these weapons means they could have only one possible use.”

Crime statistics do not record the precise type of weapon used in knife crime but senior officers acknowledge there is anecdotal evidence of the use of zombie-type blades.

A 15-year-old teenager was last month stabbed outside a south London primary school with a weapon police said was so long that it had entered the victim from the front and exited at the rear.