With the government today deciding not to reclassify cannabis to class B I read a heart rending story on the BBC website about a young chap whose life has apparently been turned upside down and nearly destroyed by the stuff. But it serves most to me to show how much of a farce the drugs prohibition system is. And the only ethical, responsible, safe solution is for radical legalisation and thereafter licensing, taxing and management of all recreational drugs in a non-criminal regime.

I don't say this because I want drugs to be widely available, though it is hard to imagine how most would become more widely available than they already are, but for two main reasons.

First, the "war on drugs" is a failure and logically cannot be won. The American Schaffer Library of Drug Policy has an informative, if not terribly easy to read chapter on how the Economics of the Black Market shows that we cannot win. Did you know, for instance, that it is possible to concentrate enough heroin for a month's supply for a single addict under a postage stamp. It's all very well hunting for trucks or boats smuggling in multiples of a kilogram, but can you imagine every single letter coming into the country being checked in such a way? Lord Birt's commission in summer on the supply side of the drugs economy concluded much the same, that the profits to be had are so great that the occasional "bust" is worth the risk.

Nor is it possible to eradicate the growing as we are attempting with very mixed results in Afghanistan. Not only is heroin routinely and cheaply synthesized (most pharmaceutical opiates are synthesized these days), but the total amounts are really tiny. With commonly achievable yields the whole supply for the UK in a year could be grown on a very small farm indeed. In the case of cannabis I believe I calculated that it would be less than a six hundred acre farm.

Second, especially for those drugs that are addictive, prohibiting something to which someone is physically and psychologically addicted will not cure them. They will have to find a supply or a substitute. Another chapter of the same Schaffer report Opiates are Addicting has all the evidence that prohibition simply cannot achieve the desired ends.

On top of this there is the cost of the criminal black market in drugs. Simply because it is clandestine suppliers get away with all sorts of manipulation and dangerous practice. Users, especially of the addictive drugs, have no recourse but to illegal and uncertain suppliers. Heroin is a biochemically relatively less harmful drug than either alcohol or nicotine.

Countless historical figures, emperors and monarchs, great politicians alike have proven that it is perfectly possible to maintain a full social and work life whilst long term dependent on opiates. So long as the supply is stable and safe. If you're not sure where your next hit is coming from, you're going to maximise the supply you've got. If you had a regular measured supply of opiates to take orally why would you want to inject, for example, with all the attendant risks? If your drug of choice was always available over the counter, why would you want to chop and change just because that's what your supplier says he's got available at the moment - hooking you into multiple-substance dependency?

We are told that up to 80% of all street and property crime is perpetrated to feed drug habits. And that a similar proportion of the prison population is there, at vast expense, on drug related crimes. And nearly all deaths associated with drug use are to do with uncertainty of the supply (overdosing because a batch is purer than you are used to for example) or lack of knowledge (such as with Leah Betts and "E" in the mid-nineties) - for nobody gives you dosage instructions with illegal supplies or medically proven information on effects, side effects and contraindications. The prohibition approach literally kills. And our legislators know this while continuing the charade that it's for the good of society that drug use be criminalised. Try telling that to parents of overdose victims.

Finally, our legislators have always known this. The story of the prohibition of opium, cocaine and marijuana in the USA is not one of harm reduction, but of moral panic based on racial prejudice. Opium was barred because it was predominantly peddled in immigrant chinese opium dens and white women were seen as being vulnerable to seduction by these chinese immigrants. Cocaine was seen as fuelling frenzied southern blacks to go on violent rape sprees attacking whites. Marijuana was blamed for making black workers in the south lazy. While these drugs were used by the upper and middle classes - Queen Victoria, Arthur Conan-Doyle and Lewis Carroll to name but a few, it was not a problem. When the proles got hold of it, it had to be stopped.

So, who is going to take the plunge? It's a very difficult issue because it is a worldwide one and in many cases we are tied into international obligations. But it is clear that the current approach does not work. However much HM Customs and Excise get hold of and temporarily drive up the price a little (leading to more crime to fund habits for the poorest users but minimal disruption to wealthy users) they will never stop the supply. And they collude in peoples' deaths. This is a price too high for a civilised, liberal society. And it must change.