The European Monitoring Centre for Drugs and Drug Addiction (Emcdda) said 300 new drugs were being examined by its experts.
And the number of new drugs continues to increase at a massive rate: 24 in 2009; 41 in 2010; 49 in 2011; jumping to 73 in 2012.
At the launch of their European Drug Report 2013, the agency said a further 20 new drugs have emerged so far this year.
Although Ireland delivered a blow to the “legal high” trade with legislation in 2010 effectively banning head shops and prohibiting a range of specific drugs, much of the trade across Europe has shifted online or onto the street.
The agency said the number of online shops continues to grow, with 693 web-based shops offering products to European consumers in 2012 — up from 314 in 2011 and 170 in 2010.
Emcdda chair Joao Goulao said the internet “has become a market parallel to the street market”.
In the biggest haul of its type in Ireland, some 23kgs of a mixture of synthetic drugs was seized in Waterford last September after being shipped in from China, where the bulk of new drugs are manufactured.
“We are faced with an ever more complex stimulant market and a relentless supply of new drugs which are increasingly diverse,” EU Home Affairs Commissioner Cecilia Malmstrom said at the launch.
Emcdda scientific director Paul Griffiths said two new drugs, 4-MA and 5-IT, had each been linked to 21 deaths.
He said consumers were “not aware” of the toxicity of the substances.
Europol, the EU police agency, said organised crime was involved in the production of these drugs.
Data previously published by the Emcdda showed Irish young people (15-24) topped the table for use of legal highs.
Some 16% said they had used the drugs at some stage in their lives, compared to an EU average of 5%. After Ireland, came Latvia, Poland and Britain, at around 10%.
In addition, a population survey in Ireland in 2010/2011 found 3.5% of adults and 6.7% of young adults (15-34 years) had used the substances.
The Health Research Board, which supplied Emcdda with Irish data, said Ireland has had “notable success in limiting the sale of new psychoactive substances through legislation”.
In relation to other stimulants, the Emcdda report said countries with a high-prevalence of cocaine use, including Ireland, have seen a reduction in usage.
It noted a “greater availability” of MDMA, known as ecstasy, in Europe and that this might encourage renewed interest in the drug.
Gardaí have told the Irish Examiner that demand for ecstasy is up, with one of the biggest seizures in recent years occurring last weekend, with a bumper haul of around 100,000 tablets in north Dublin.