Deaths caused by legal highs have risen by almost 600 per cent in three years, according to a new report.
One expert warned users that experimenting with such drugs is like “dancing in a minefield”.
Post mortem tests showed that 97 people were found with these drugs in their system in 2012, up from 12 in 2009.
Almost two thirds of legal high related deaths were directly caused by the substances, with numbers rising from 10 in 2009 to 68 in 2012.
Data published in the National Programme on Substance Abuse Deaths (NPSAD) report was compiled from coroners’ reports submitted to St George’s University of London.
Professor Fabrizio Schifano, spokesman for the NPSAD said: “The worrying trend is that these type of drugs are showing up more than ever before.
“Clearly this is a major public health concern and we must continue to monitor this worrying development.
“Those experimenting with such substances are effectively dancing in a minefield.”
The proportion of deaths involving cocaine and ecstasy-like drugs has also risen since 2010, the report showed.
The figures were released as the Government announced tougher penalties for ketamine use.
The party drug, also used as a horse tranquilliser, will be moved from a Class C to Class B drug and illegal possession could result in up to five years in jail.
The father of 18-year-old Ellie Rowe, who died from taking ketamine, supported the upgrade.
Speaking of the “intelligent, caring” teenager, who was aiming to become a lawyer, he said: “It was one act of stupidity that destroyed our family”.
Last year some 120,000 people took ketamine, also known as special K.
The NPSAD’s report follows crime prevention minister Norman Baker’s review of legal highs that seeks to boost police and law enforcement agencies’ powers.
Baker said: “I am determined to clamp down on the reckless trade in so-called legal highs, which, as this report shows, has tragically claimed the lives of far too many people”.
The report also warns that legal highs have undergone little or no human testing so their health effects are virtually unknown.