Increasing numbers of people are dying after taking ‘legal highs’ in the UK, researchers have found.
In recent years, the number has risen from 10 in 2009 to at least 68 in 2012, pot-mortem figures from the National Programme on Substance Abuse Deaths.
Legal highs are designed to mimic the effects of illegal drugs, and are chemically different enough not to be covered by the law.
Many legal highs are openly sold on websites and high streets in the UK.
John Corkery, co-author of the report, told the BBC: "In a fair proportion of cases, for example (the now banned) mephedrone, we are aware there was only one substance taken and it's quite clear that's caused the effects which led to death.
"But in many cases it's a combination of other substances including alcohol but particularly stimulants like cocaine amphetamine and ecstasy."
Drugs minister Norman Baker has admitted it is a “challenge” keeping up with the fast moving industry.
A review into current laws on legal highs is expected to report back in the summer.
He said: “The reality is, we’re chasing the chemists.
“There are people elsewhere in the world who are busy creating drugs which mimic illegal drugs… In order to produce a drug which is temporarily legal until we ban it. But maybe as dangerous, or more dangerous than the drugs that are already controlled.”