A drug information charity has claimed that drug addicts are making increasing use of a tranquilliser once known as "mother's little helper" as an alternative to heroin.
Increasing numbers of people are abusing diazepam, which is better known under its defunct brand name Valium, according to DrugScope.
The tranquilliser could be growing as a cheap alternative to heroin because supplies of the drug have suffered a recent slump in purity. Addicts are now combining diazepam with strong alcohol or methodone to ease the effects of withdrawal from crack cocaine, the charity warned.
DrugScope found that usage was rising in 15 out of 20 town and cities across the UK covered by the research, with a 10 milligram dose of diazepam costing just £1.
Martin Barnes, the charity's chief executive, said: "The rise in the use of diazepam is concerning, particularly as drug users face a high risk of overdose when using the drug in combination with other drugs such as methadone and alcohol.
"With the proliferation of counterfeit diazepam comes unpredictable quality and strength."
He added: "A heroin shortage might instinctively appear a positive development, especially as it can lead to more people entering treatment, but it can bring its own problems."
"As an ex heroin user (now on methadone), I have not seen an increase but I have noticed that drug users use all of these drugs, whether heroin is in short supply or not. Even if there is a shortage it is never more than a few days. The more popular drugs I have seen used are anything with codine (even nightnurse) to get to sleep, also jellies. People will even wait outside chemists to buy methadone" – David Bremner, Aberdeen