Dealers are lacing cannabis with highly addictive heroin to get users hooked on the deadly drug.

Secret off-the-record discussions between police and a supplier in London have revealed how recreational drug users are being tricked into becoming addicted to Class A drugs.

Officers fear it could lead to a surge in addicts in Brighton and Hove, which is already known as the drug death capital of England.

They believe cannabis users are becoming accidentally dragged into heroin use.

It follows the discovery that potent, paranoia-inducing cannabis, known as skunk, was being sold in large quantities in Brighton and Hove last year.

Detective Sergeant Hari McCarthy, of Sussex Police, said: “People buy it thinking it’s just very strong weed.”

“It’s not being sold as skunk, just good weed, but it’s an easy way to get users hooked on heroin.”

She added that dealers mixed various chemicals with cannabis before selling it, including tranquillisers and even urine.

There are believed to be 2,300 heroin addicts in Brighton and Hove.

The revelation was made during an inquest in Brighton into the death of 34-year-old electrician Lee Donlan from a heroin overdose.

Clinical and forensic toxicologist Peter Sharpe confirmed that taking mixtures of drugs was becoming more and more common in Brighton and Hove, in particular the highly dangerous combination known as speedballing.

He said: “There’s a mixture called speedballing – it’s heroin with a bit of cocaine, usually injected into the arm or ankle.

“People like the mixture of heroin and cocaine because the cocaine reduces the low that comes after the heroin.”

The combination has become well-known because of the famous Hollywood lives it has claimed.

Promising actor River Phoenix died aged 23 in 1993 after injecting himself with a speedball in the Viper Room nightclub in Los Angeles.

Blues Brothers star John Belushi also died in Los Angeles after he took the drug aged 33 in 1982 while comic actor Chris Farley died after taking it in 1997.

Although no needles were found next to Mr Donlan’s body when it was discovered at the flat in Norfolk Mews, Brighton, Dr Sharpe said the mixture of both cocaine and heroin in his blood was suggestive of speedballing.

Mr Donlan had an amount of alcohol in his blood equivalent to about six pints of beer as well as cocaine and 0.13mg per litre of heroin.

He said: “Between 0.1mg and 0.2mg is typical of a heroin death.”

The father-of-one had not been known by his friends or family to be a heroin user and Karen Henderson, the deputy assistant coroner for Brighton and Hove, said it may have been the first time he had tried the drug.

His uncle, Geoffrey Wilcock, described Mr Donlan as a “gentle giant” and said he had met up with him a week before and he showed no signs of being a drug user.

Dr Henderson criticised Sussex Police for the investigation into Mr Donlan’s death.

Despite finding more than 7g of cocaine under his mattress police did not deem the death to be drug related until the postmortem results came through by which point she said vital evidence may have been missed.

DS McCarthy agreed it was unusual that nobody who attended the scene deemed it to be a drug related death and no investigation was carried out into Mr Donlan’s phone records to track down a potential supplier of the lethal cocktail.

Addressing DS McCarthy, Dr Henderson said: “Your lack of ability to find evidence is seriously compromising to this inquiry.

It is unsatisfactory on every level.”

A 999 call was made by Mr Donlan’s flatmate, Finlay Finlayson, at about 12.55pm on March 6.

Paramedics were called but he was declared dead.

After his body was removed duty officers attended the scene but despite finding a bag of white powder no more senior officer was called as the death was not deemed to be drug related.

DS McCarthy said: “In hindsight I should have attended the scene.”

Police have said they will look into the case again.

Dr Henderson recorded an open verdict.

After the inquest a police spokeswoman said: “There was an investigation at the time to seek to identify how he came to be in possession of and subsequently take the heroin but at the time police were not able to establish those facts.”