Melissa Kite, in her argument against the legalisation of drugs, says: "What is needed, more than ever in our 'everything goes' society, is a bit of restraint every now and again" (The illogic of legalisation, 17 September). This "just say no" approach to the problem is so discredited that it is now frequently cited as a case study for a failed drug prevention campaign – and hence no longer used as a slogan even in the United States.

She asks us to think of "not only active addicts who are locked in compulsive drug use, but also those millions of potential addicts, most of them children, who have not yet picked up their first drug and could go either way". This ignores the fact that current, unregulated policies expose British youngsters to the dangers of a criminal market, as well as to the possibility of acquiring a damaging criminal record. Drug dealers don't ask the age of their clients, and their motivation is profit. Young people now have easy access to unregulated, potent and possibly adulterated cannabis.

Over the years government has tried many variations of the prohibitionist approach, and the outcome has been an increase in supply of very potent cannabis varieties like skunk, rising violence, soaring arrests and the spawning of new synthetic cannabis substitutes created with the intention of bypassing the law.

After decades of failure it's time to consider a different approach based on pragmatic common sense and scientific evidence – which is the aim of our report, Licensing and Regulation of the Cannabis Market in England and Wales, which sparked Kite's article.

Why is Kite so afraid of research? It is evident that the war on drugs has failed at every level. Governments have in effect handed over one of the world's most profitable businesses to criminal cartels which pay no taxes, are motivated purely by profit, and which corrupt officials at every level of administrations around the world.

Kite says she doesn't "understand at all what decriminalisation of drugs will do for addicts". However, the evidence from countries with more liberal drug policies, such as the Netherlands and Portugal, shows that this approach allows public health to be prioritised over punishment. There are savings for the criminal justice system, as well as public health and educational gains. Doomsday scenarios of exploding levels of use following decriminalisation have not materialised.

Kite incorrectly says I claim that "200,000 people around the world die from illegal drugs compared with five million from tobacco". This is completely false, as cannabis itself does not kill anyone. The estimate comes from the use of all illegal drugs, including heroin, cocaine, methamphetamine and others. People should not be prosecuted for a victimless crime. Fifty years of the "war on drugs" has proved that prohibition doesn't work. The young and vulnerable remain completely unprotected.

We need to rethink our approach to the control of currently illicit drugs. As long as people seek substances to change how they feel there will always be a market for them; and where there is a market, there will always be someone to meet its demands. Therefore the government should work out how to control this market in order to minimise harms, to protect people and educate them – not criminalise them.

Amanda Feilding is founder of the Beckley Foundation The full version of this article appears on www.theguardian.com/commentisfree If you wish to respond to an article in which you have featured, email response@theguardian.com or write to Response, The Guardian, Kings Place, 90 York Way, London N1 9GU. We cannot guarantee to publish all responses, and we reserve the right to edit