DRUG abusers in Wirral are putting their lives at risk with a terrifying new threat from drugs bought on the internet from sources overseas.

A dramatic decline in the purity of "street" heroin has seen addicts augmenting their habits with benzodiazepines, themselves highly addictive. They are prescription-only tranquilisers in the UK, but available over the counter in many countries.

Steve Kelly, a manager at Birkenhead-based Advice, Recovery, Counselling and Health (ARCH) said: "We are highly concerned with this worrying new development. Our service users are now taking 'benzos' to enhance the effects of heroin, which is not as strong as it was two years ago.

"Often they will top up this cocktail with high-strength beers or ciders. In this way they are acquiring a triple habit. A lot of product comes from the Indian sub-continent and could contain anything. It's a deadly gamble."

ARCH provides help for all drug and alcohol users on Wirral. Benzodiazepines can impair liver function, cause nausea, compromise heart function and cause death.

Mr Kelly said: "Coming off benzodiazepines too suddenly is highly dangerous in itself. Users frequently go into convulsion similar to epileptic fits. And these can kill.

"The only safe way to stop is gradual managed reduction under medical supervision."

The problem has arisen rapidly. What began as a few individuals importing benzodiazepines for personal use is now a sophisticated international criminal enterprise played for big money and high stakes.

A Merseyside Police spokesman said: "Benzodiazepine is a class C controlled drug as classified under the Misuse of Drugs Act and listed as a prescription-only drug under the Medicines Act.

"Anyone found in possession of this substance, without a prescription from a doctor, is committing a criminal offence and can be arrested an prosecuted."