University of Leicester researchers also claim that despite new legislative controls over drugs such as mephedrone and other substituted cathinones, there is some evidence to suggest that little has changed and banned substances are still being sold online under a new guise.

Dr John Bond and Tammy Ayres from the University's newly launched Alec Jeffreys Forensic Science Institute make the claim in a study to be presented at a seminar for the Department of Criminology on Friday (Dec. 7).

The study, published in the British Medical Journal, analysed the constituents of 22 products marketed as research chemicals, plant food or bath salts purchased from five different internet sites. They aimed to ascertain what is in legal highs, their legality and safety, while considering the potential impact these synthetic substances might be having on public health and the criminal justice system.

Their findings illustrate that illegal cathinones are still being sold online as legal alternatives to illegal substances -- a fact also used as a marketing tool by the suppliers in this research.

Tammy Ayres, of the Department of Criminology, said: "Recreational drug use has changed to include a range of substances sold as 'research chemicals' and 'plant food' but known by users as 'legal highs' -- legal alternatives to the most popular illicit recreational drugs.

"The number of new legal highs appearing on the market is continuing to grow and the number of online shops selling these substances has trebled since 2010, the majority of which are in the UK.

"This raises concerns over the health of those buying and taking these substances as little is known about their long term affects. There are only a handful of studies that have bought and tested legal highs available to purchase off the internet for banned cathinones.

"This research demonstrates that drugs cannot be legislated out of existence and illustrates that prohibiting these substances does not stop their supply or their use."

Dr John Bond, from the Department of Chemistry, said: "Products are frequently given new names and marketed as superior, but legal, alternatives to the banned substances they purport to replace. It is not known how many of these new products contain newly synthesised and legal chemicals and how many continue to contain illegal substances like mephedrone, which has been linked to a number of deaths.

"Health professionals have a complete lack of knowledge about the short and long term effects these substances have on those presenting themselves at GP's surgeries or hospitals. Even if they take the packaging with them, there is nothing on it to assist in understanding what it is that the patient has taken.

"These substances are not legal, it is simply that the companies selling them purport them to be harmless and legal when the opposite is true."

Dr Bond added: "This work reflects the new launched Alec Jeffreys Forensic Science Institute's contribution to informing the police and health agencies in the UK on the current state of availability of these substances."

Tammy Ayres is currently bidding for further funding to pursue this work for the benefit of the police, health service and, most importantly, the users of these substances.