The deaths of two young men in Scunthorpe last Monday that have been linked to the new "legal high" mephedrone (colloquially known as plant food, meow meow, m-cat, or bubbles) has raised a great deal of public concern and loud calls for it to be made illegal. I support the government's position that to rush into controlling mephedrone is premature, as previous claims of fatalities from this drug have turned out to be false alarms. To make it illegal without proper evidence of harm would be wrong and might have unwanted consequences, such as a switch to more dangerous drugs or alcohol. The European Monitoring Centre for Drugs and Drug Addiction is reviewing the situation and will report in July.

The threat of new drugs being available via the internet emerged in Brain Science, Addiction and Drugs, the 2005 review from Foresight, the government's future thinktank. Recent years have seen the development of GBL, spice, BZP and now mephedrone, a short-acting stimulant with effects similar to amphetamine, though it is less well studied. There was widespread use in Israel earlier in the decade but little evidence of immediate or enduring harm, though high doses are potentially dangerous especially if used with other drugs and alcohol.

Its use has increased greatly due to growing availability, and a legal status that means users do not run the risk of criminal convictions. Criminalisation would allow police and customs officers to act on dealers though this will not be easy, and the risk is that young users will be an easier enforcement target. Moreover there is the likelihood that new legal drugs will emerge to fill the void, just as mephedrone has with BZP, and that these may be more harmful.

What are the alternatives? One approach would be a new class in the Misuse of Drugs Act – the class D model, adopted in New Zealand to deal with BZP. This is a holding category where drugs can be put before they are well understood: sales are limited to over-18s; the product is quality-controlled so users know what they are getting, at doses limited as far as possible to safe levels; and it comes with health education messages. Society can limit sales and collect data on use.

Manufacturers and shops that disobey these regulations are punished, and the young are protected, but not criminalised. Last summer the Advisory Council on the Misuse of Drugs, when under my chairmanship, suggested this approach in response to the growing use of spice and BZP. It was rejected, they were both made class C, and possibly as a consequence young people began to turn to mephedrone.

Another approach that should seriously be considered is to make available testing facilities so that people can check what they have brought and so ensure as far as possible that they use appropriate doses and apply the best safety approaches. Testing is used in the Netherlands and some Australian states, with seeming value in harm reduction.

The third is education: drugs are rarely intrinsically harmful if used in a safe way. Many young people use the most popular legal high – alcohol – in a highly dangerous fashion. Recent deaths from legal highs, particularly those of Hester Stewart and the Scunthorpe pair, occurred in the context of drinking. Alcohol dissolves judgment of harms and encourages risky behaviours including drug taking. Some drugs interact with alcohol to form more dangerous substances – for example, cocaine is converted to cocaethylene, which is more toxic to the heart.

Finally we need to understand the reasons why young people are so interested in highs – legal or otherwise. Addressing the cause of drug use might help us better reduce its harms.

• A minor amendment was made to the penultimate paragraph of this article on 22 March 2010