John Huffman, 84, created a synthetic version of cannabis - now known as Spice - in his lab.

A DRUG at the centre of an epidemic where addicts are left wandering the streets like ‘zombies’ was innocently invented by an American scientist while examining the effects of cannabis on the brain.

John Huffman, 84, created a synthetic and extremely potent version of the drug – now known as Spice – in his lab at Clemson University in South Carolina in the 1990s.

But years later variations of his compound are blighting the lives of young people across the UK as shocking pictures have shown users slumped on pavements and reduced to trance-like states.

The father-of-four claims he was "experimenting for good" and "couldn't have known" what would happen to his research.

He now wants Spice banned globally - but still believes cannabis should be legalised.

The scientist was investigating how receptors in the human brain respond to the key ingredient of cannabis - tetrahydrocannabinol (THC) when he created the synthetic compounds.

He named each one with his initials JWH followed by a number and wrote detailed research to ensure he received further grants for his work.

His discoveries went on to be copied numerous times and he says there are now 465 variants of JWH "cannabinoids", which have spread around the world.

Mr Huffman told the Sunday Times: "Could I have known? No. Marijuana has been around for hundreds of years, its effects are well known and you cannot kill yourself with it.

"You can kill yourself with the synthetics.

"People have asked why I published... Well, if you want to get grants renewed, you have got to be published."

He added that it was "strictly research."

Mr Huffman has previously spoken out about how Spice should but banned but wants marijuana to be legalised.

He told ABC News in 2011: "I talked to a marijuana provider from California, a doctor, a physician, and he said that in California, that these things are not near the problem they are in the rest of the country simply because they can get marijuana.

"And marijuana, even for recreational use is quite easy to get in California, and it's essentially decriminalised. And marijuana is not nearly as dangerous as these compounds."

All variants of Spice were made illegal in the UK last May and there has been 72 prosecutions with 332 shops banned from selling it and 31 shops closed down.

The synthetic form of cannabis has been sweeping the country

It has not halted the trade, with the Sunday Times finding more than 40 websites offering ­different forms of the drug including one prepared to sell £80,000-worth without a check.

Disturbing footage has shown prisoners in British jails getting high on Spice which has been smuggled in.

Other images have shown people slumped across pavements and even one standing dazed in the middle of the street in a scene likened to The Walking Dead.

It comes as cops battling the Spice epidemic sweeping through Manchester have made 22 arrests in a fresh crackdown.