The fashionable party drug mephedrone has been linked to up to 98 recent deaths in Britain, government advisers have warned in calling for tougher action to combat the proliferation of legal highs.
The Advisory Council on the Misuse of Drugs said unscrupulous manufacturers made a mockery of the law by falsely advertising addictive substances as "plant food" or "bath salts".
Its chairman, Professor Les Iverson, said young users of "designer drugs" were playing "Russian roulette" with their lives - and the effects were already being seen in hospitals.
"We are not seeing just a nice party drug but something that can kill."
Iverson released figures showing that in the past two years mephedrone had been confirmed as a factor in 42 deaths and had not been ruled out as contributing to a further 56.