Dozens of new synthetic drugs, often marketed as "legal highs" on the internet and made in Asia, emerged last year, replacing traditional, plant-based drugs in Britain and Europe, according to official figures.
The European Union's Monitoring Centre for Drugs and Drug Addiction has highlighted the new trend at a time when the use of cannabis, cocaine and heroin is slowing.
"The drug situation may now be in a state of flux, with 'new' problems emerging that challenge current policy and practice models: new synthetic drugs and patterns of use are appearing, both on the illicit drug market and in the context of non-controlled substances," the centre said in its annual report.
The centre reported that there were now more than 280 new drugs in circulation, with 73 appearing in the past year alone.
Many of them were made from chemicals designed to mimic the effects of cannabis.
British figures published last week showed that the number of people dying from banned "legal highs" had quadrupled in the past five years.