Is cannabis very harmful? Don't be a dope

The Government's message on cannabis has been unclear

The Government's drugs policy is a mess. Who says so? No less an authority than Professor David Nutt, the Government's chief adviser on drugs, who has been sacked for his temerity. His dismissal has been followed by the resignations of another member of the Advisory Council on the Misuse of Drugs (ACMD), which he chaired. Prof Nutt's offence was to say that cannabis causes less harm than alcohol and tobacco – not just to the health of the individual consumer but also in a wider sense, especially the violence associated with binge drinking. Since this is a fact, attempts to traduce him as the nutty professor are absurd.

He did not say cannabis is harmless; certainly today's stronger varieties are associated with psychotic behaviour. Nor did Prof Nutt suggest cannabis should be legalised. His point was that if you are going to have a classification system based on relative harms, then it is a bit odd to put cannabis on a par with more dangerous substances. Those who dispute this do so because they do not like the louche lifestyles of recreational drug users; but disapproval does not change the facts.

Prof Nutt's mistake was to imagine that this was a scientific issue when it is a political one. Government ministers believe that the public will not accept anything that looks like they are being soft on a particular drug, especially the most widely used variety. This is simply not true. A YouGov poll, one of the largest surveys conducted in this country on drugs policy and carried out for the Royal Society for Arts, Manufactures and Commerce (RSA) drugs commission, on which I sat, showed that most people would be happy to see the personal use of cannabis decriminalised or penalties for its possession lowered to the status of a parking fine.

However, since this is not going to happen any time soon, you have to ask why the Government moved cannabis from B to C in the first place. This story is an object lesson in how to mess things up and finish in a worse position than where you began.

The classification system was laid down in the 1971 Misuse of Drugs Act to provide a matrix of potential and relative harms linked to a penalty scale. That is where the law stood until October 2001, when David Blunkett, then Home Secretary, announced that he wanted to move cannabis from B to C. Since the law then specified that possession of a Class C substance was a non-arrestable offence, this meant the police would be free to deal with "harder" drugs, such as heroin and crack cocaine, which caused most of the crime problems.

The Advisory Council on the Misuse of Drugs agreed with Mr Blunkett and cannabis was duly downgraded in 2004.

In the first year, there was no increase in use of cannabis, and arrests for possession fell by one third, saving an estimated 199,000 police hours. It did not take long, however, for the aims of the policy to be lost in a fug of confusion. Shortly before the general election in 2005, a new Home Secretary, Charles Clarke, asked the advisory council to carry out another review – a cynical device to get Labour through the election campaign. The council, unsurprisingly, reached the same conclusion as it had the year before and, safely back in office, Clarke agreed to keep cannabis in Class C.

The classification system itself was then questioned by the Commons Science Select Committee. It produced a table of harms, placing alcohol fifth on the list, ahead of some class A drugs, while tobacco was ninth. Cannabis was 11th. Interestingly enough, when people were asked by YouGov to do their own non-scientific drugs classification, they also put alcohol and tobacco ahead of cannabis.

Then Gordon Brown became Prime Minister and decided he wanted a drugs policy showing he possessed a "moral compass". So the Advisory Council on the Misuse of Drugs was sent off to think again, a disgraceful use of an independent advisory body. Once more, it recommended cannabis should be Class C, but was overruled by Mr Brown, who had made up his mind to return it to Class B, whatever the scientific evidence.

There is an argument, and one that is not confined to far-out libertarians, that if cannabis, heroin and cocaine were legally available they could be controlled much more effectively and their supply – which has expanded despite massively expensive efforts to shut it down – removed from the hands of criminals. But that is not going to happen. Any government that proposed it would be crucified. Furthermore, there are international obligations operating through the United Nations that Britain, as a signatory, must uphold. These require certain drugs to be illegal and in this country are enshrined in the Misuse of Drugs Act 1971.

In that case, it behoves governments to implement laws in as effective and coherent a way as possible, which means sending out clear messages and deploying punishments and penalties consistently. Yet in recent years, where cannabis is concerned, the message has been anything but clear. Indeed, ministers have made such a pig's ear of the law that you have to wonder whether they were smoking the stuff themselves.