A youth survey which revealed that soaring numbers of schoolchildren are dabbling in drugs has prompted calls for urgent action.

Nearly half of 15 and 16-year-olds in Britain have tried illegal drugs, with 38 per cent of girls and 43.6 per cent of the boys saying they had used cannabis, according to the most comprehensive survey into teenage drug use undertaken.

Experimentation with every other kind of recreational drug, except alcohol, has increased since 1989 when a similar survey of 7,000 young Britons was conducted by the Health Education Authority.

Drugs advisers and academics say the survey, funded mainly by the Alcohol Education and Research Council and part of a European project involving 26 countries, shows that expensive health promotion campaigns are missing the point. They want more schemes based on limiting the harm drugs can cause rather than on trying to eradicate them.

Researchers from Edinburgh University found that, of the 7,500 youngsters questioned, virtually all had consumed alcohol and one in three were smokers. These statistics provoked renewed calls for tougher controls on cigarette advertising and the marketing of drink, in particular the new breed of alcoholic “soft drinks”.

According to the survey, which was conducted in 79 private and state schools, teenagers are drinking more frequently but no more in total than the same age group seven years ago. The number of boys smoking has remained constant but more girls are turning to cigarettes, possibly as an appetite suppressant.

The greatest concern raised by the survey is the widespread use of the cheaper drugs. Apart from cannabis, one in five said they have tried glue or solvents, while 12.3 per cent of girls and 14.5 per cent of boys said they have taken amphetamines.

Three times as many boys and girls have taken ecstasy (Pounds 5-15 per tablet), the drug of the late 1980s’ dance culture.

Heroin and cocaine are also more popular, although they are still beyond the means of most teenagers.

For the first time the survey looked for differences in England, Wales, Scotland and Northern Ireland. It found drug-taking was highest among Scottish boys (59.9 per cent) and lowest in girls from Northern Ireland (18.4 per cent).

Professor Martin Plant, one of the report’s authors, said it proved the need for a more sophisticated approach to teenage drug abuse.

Anti-drugs campaigns and advisory services, which have attracted millions of pounds of state investment over ten years, have failed because they are outdated and fundamentally flawed, Professor Plant said.

Professor Plant believes that price, availability and peer pressure explained the rise in teenage drug use. He urged the Government, the medical profession and teachers to follow the lead of drugs agencies which have adopted a policy of “harm minimisation”.

This pragmatic approach focuses on reducing the dangers of drug use and found favour with drugs groups trying to slow the spread of the HIV virus in the 1980s.

“We need to stop further abuse and limit the harm done. We already do this with alcohol, by accepting its common use and abuse, but by pointing to the dangers for drivers, industrial workers and pregnant women.”

However, there are legal restrictions regarding the treatment of under-16s which make it harder for drugs groups to use this approach with children - they can, for example, give older addicts clean needles.

Lifeline, the Manchester-based drugs advisory group, said the survey confirmed a trend identified in recent research by the Health Education Authority in Manchester and Liverpool. This had identified a sharp increase in teenage drug-taking, especially of cannabis, which has become so common that police seldom prosecute users.

Jez Buffin from Lifeline said many young people were concerned about a drug’s value for money not its illegality. Young people were clued up and knew the best and cheapest ways of getting high, he said.

He said that as the age of drug users continues to fall, parents are the key to developing an effective deterrent. They should arm themselves with the facts about drugs and talk to their children. A survey to be published next week by Boots, the high-street store and pharmaceutical company, will show that 86 per cent of parents do not know much about drugs.

More than half of parents of seven to 21-year-olds questioned were concerned that their children might become addicts, and a further 39 per cent were worried drugs may kill them. Nearly half said they had not discussed drug abuse with their children in detail.

The Edinburgh survey has increased pressure on the Government to develop a more effective prevention policy. The Department of Health is spending Pounds 33.4 million this year on treatment and prevention, of which Pounds 5m goes on publicity and Pounds 1.5m on a helpline.

Drug awareness in schools is taught from the age of 11 and the Department for Education and Employment has sponsored 18 anti-drugs projects since last year.