spice homeless
The synthetic drug Spice is becoming very popular with Britain's homeless population.Getty

New strains of Spice, a synthetic version of cannabis, are turning Britain's streets into the "walking dead".

Shocking images have circulated social media this week and show suspected drug users slumped over, glazed and resembling zombies in several cities across the UK.

The former legal high was banned last May as part of the Psychoactive Substances Act, however, the law has pushed the trade underground and into the hands of drug dealers.

Now Spice has reportedly become a hit with addicts and the homeless population as a cheaper alternative to heroin – costing as little as £10 ($12.17) a gram in cities like Leeds and Manchester.

Julie Boyle, a support worker at Lifeshare, a homeless charity covering Manchester, told The Times she believed that Spice was more dangerous than heroin.

"It's harder to come off Spice than it is to come off heroin," she said. "It makes vulnerable people more vulnerable. This thing at the moment that's freezing people like statues… It's a new strain that's been around for about 10 days, it makes them in a catatonic state."

Spice is also popular as its easy to take, as it does not require injecting, as it is sprinkled into rolled-up cigarettes. However, it lacks the pungent odour of cannabis.

Spice is well documented as causing havoc in Britain's prisons, but its spread to the black market on streets since it was banned is relatively new and raises further complications for law enforcement and drug charities.

A Spice user named Carl from Manchester told the Daily Mail he has been addicted ever since buying the drug in a legal high shop.

"It's awful to come off it," he said. "You rattle. I've tried to get off it, but it's harder than gear [heroin]. I smoke this because it's better for me than injecting with needles – better for my health."

As he smoked the drug unfazed in front of the reporter, he said: "I'm starting to feel woozy. I can feel all my problems going away."

Gavin Rodda, a bus driver from Wrexham, north Wales, was among the people to share images of Spice users online after constantly being confronted with addicts at the bus station.

"These pictures are shocking but it's the reality of everyday life for the addicts that use there," he told The Times.

"I want people to see this and find a solution to the major drug problem that Wrexham has.

"Is it really going to take a death of an addict to make a change? I hope not."