Cocaine
Cocaine is a highly addictive narcotic iStock

UK cocaine users have been warned against the rise of super-strength product sold on the dark web for as little as £40 ($54) a gram.

Punters can by 85% purity "Peruvian flake" from an anonymous online seller with cryptocurrencies such as Bitcoin.

But there are fears the drug will overwhelm customers who are used to vastly inferior UK street cocaine, which can be as weak as 20% purity.

Speaking about the new grade-A product, one online drugs tester said: "This is very potent and users should be very careful with initial dosing – 100 MG will not be fun.

"A UK user, who thinks they are experienced but buys low-quality cocaine in pubs and takes a 300MG dose, could end up in A&E.

"Please don't be Billy big b****cks and try and impress your friends that you have the best cocaine available. "Seeing your mate foaming at the mouth is no fun."

The comments were unearthed by that Daily Star on a subreddit where drug users meet to discuss the quality of narcotics sold on the dark web.

The UK's reputation for low purity cocaine has been challenged in recent years by the emergence of a two-tier street market in which 40% strength "pub dust" is sold for around £40 a gram, while 60-70% gear is traded at around twice the price.

However, the emergence of the dark web as a mainstream drugs market, no longer the preserve of computer experts, has enabled users to access higher quality cocaine at lower prices.

In May 2017, super-strength cocaine caused two deaths in East Sussex. In 2016, the latest figures available, cocaine-related deaths reached an all time high in England and Wales, totalling 371 fatalities, up 16% from 2015 and 167% since 2012.

Dr. Adam Winstock, author of the Global Drugs Survey, said of his 2016 report: "This year's study shows that increased drug purity is leading to a surge in admissions to A&E departments across the UK. We need to educate users about purity levels and the impact that they have on the bodies.

"Another concerning development is the UK appears to lead the world in the rise of purchasing drugs on the darknet. The darknet allows dealers to be anonymous, taking away all accountability and it is a concern that the UK currently is outpacing much of the world in its rush to buy drugs this way."

Drug users can meet dealers anonymously on the dark web, an underbelly of the internet which affords organised criminals the opportunity to trade anything from weapons to child prostitutes.

AlphaBay and Hansa – two of the most prominent marketplaces for drug dealing – were shut down by US authorities last year. However, several other portals exist that can be easily accessed by anyone with an internet connection.

The drugs are sent in anonymous packages to the end user's address.

Once just the narcotic of choice for well-heeled Metropolitan elites, cocaine is now popular in all corners of the UK. A 2016 report from drugs think tank Drugswise noted: "While cocaine still retains something of a 'champagne lifestyle' image, on the basis of various [police] officer reports, it is well embedded (along with alcohol) in the night time economy of relatively deprived areas such as the small towns of Staffordshire."