The government delegate responsible for the National Drugs Plan, Carmen Moya, said yesterday that: "legalising cannabis would be totally irresponsible," and went on to say that the health authorities are obliged to protect the health of the public.

She was responding to demonstrations staged by legalise cannabis organisations yesterday in Madrid, Málaga, Vigo and León, which Ms Calvo said only represented a small minority of the population, adding that legalising the drug does not constitute a "social necessity."

"It is not appropriate to contemplate legalising a substance that carry health risks to those who use it," she said, perhaps forgetting that both tobacco and alcohol are legal.

Ms Calvo went on to point out that adolescents are most at risk from possible attention deficit and short-term memory problems, and pointed out that habitual users often play truant from school, get worse marks than their peers, and generally fail to fulfil their potential.

She also pointed out that it is dangerous to drive under the influence of the drug, which "can triple the risk of pyschosis, especially in the most susceptible."

What is worse, according to recent research, among 14-18 cannabis users, 92% also drink alcohol, 65% smoke tobacco, 14% take cocaine, and 7% take other stimulants.

When asked whether the government was considering stiffer penalties for cannabis users, Ms Calvo said: "The Law must be obeyed."