The first time I came across the sickly sweet smell of cannabis was more than 40 years ago in Notting Hill.

As a young reporter, I did a story about drugs parties at which dealers took over houses for a night and charged admission for the potent mixture of pot and pop.

Questions were asked in the House of Commons about this esoteric drug and while I didn't exactly achieve my allocated 15 minutes of fame at this point, maybe I had 15 seconds.

Even five years later, when I arrived in Brighton, possession of cannabis (then called Indian hemp) was guaranteed a page lead in The Argus or an item on the 6pm Southern Television News.

I was reminded of this at the weekend when the big beach party was staged in Brighton. The prevailing aroma at the time, and for many hours afterwards, was a mixture of urine and cannabis, not a pleasant combination.

Back in the Sixties, police were strict about drugs and possessing cannabis was regarded as a serious offence.

Now, thanks to Home Secretary David Blunkett's downgrading of the drug, cannabis is being smoked openly on the streets and on Brighton beach.

Mr Blunkett's decision has created a curious anomaly. Smoking or keeping small amounts of cannabis is accepted, tolerated or ignored.

Yet anyone who supplies exactly the same drug is liable to be prosecuted.

Does this matter? Not a jot, according to many influential people including the Home Secretary's advisers and a posse of senior policemen who believe cannabis is harmless and the law was being so widely abused it was becoming a mockery.

Many would go further and legalise cannabis. Some would even legalise all drugs, saying this would at a stroke reduce crime.

I can see the logic behind this argument but I do not agree. While many people who smoke cannabis have suffered no ill-effects, there is evidence that prolonged use of the drug can be harmful.

Some of those who started smoking pot in the Sixties have reached a state of continuous advanced lethargy. Psychiatrists say there is growing evidence cannabis aggravates mental conditions such as schizophrenia.

The Brighton Pavilion MP David Lepper also makes the point, which has strong medical backing, that smoking cannabis is as harmful to the lungs as cigarettes and carries a considerable cancer risk.

Many cannabis smokers say they never touch anything harder but I would bet if you asked them for truthful answers, the majority will have at least dabbled with danger. There is no doubt that cannabis is a gateway to hard drug addiction.

People such as the former drugs czar Keith Hellawell, who resigned because of the Government's attitude, say they have never met heroin or crack cocaine addicts who did not start on cannabis.

There is contradictory evidence from The Netherlands about the effects of a more liberal policy towards drugs. Some say it is the answer and others contend it has led to increased addiction.

It seems indisputable that a tough line on drugs has been effective in Sweden although whether what works well in a small, law-abiding Scandinavian country could be transferred to the UK is doubtful I can see why David Blunkett, a practical politician, made the move he did but the long-term consequences could be dire.

The trouble with cannabis, as with cigarette smoking, is the consequences are felt many years afterwards and by then it is almost certainly too late.