Those who do drink are likely to drink more, with an average weekly intake just under a pint of beer, compared to half that in 1990.

Almost a third of smokers had more than 10 cigarettes a day, while 70% smoked at least 20 a week.

The biennial study looked at 11 to 15 year olds in England and 12 to 15 year olds in Scotland, and for the first time looked at drug use in this age group.

Eileen Goddard of the Office for National Statistics, who worked on the report, told BBC News Online: "We've been gathering these figures since the early 80s, but until recently the prevalence of smoking and alcohol consumption has been increasing - now they've dropped.

Off licences were more popular than pubs with teenagers

"But it's difficult to tell whether it's a long-term trend, especially with this age group as they can be so changeable."

The overall figures also showed that in Scotland, 18% had used illegal drugs at least once, as had 13% of the children in England.

However, drug use increased with age - the figures shoot up to 39% and 33% at 15.

There was also evidence that smoking or drinking led to drug use - in England, for example, 63% of regular smokers had used drugs, compared to one per cent of those who had never smoked, with a similar trend among drinkers.

Professor Liam Donaldson hopes the trend will continue

"That's a huge difference - a lot of it's to do with the fact that the drug they are likely to use is cannabis, which is smoked, so they're used to the method of taking it," Ms Goddard said.

Cannabis was offered to 34% of the children surveyed in Scotland and to 26% in England, and five and four per cent respectively had been offered heroin.

Professor Liam Donaldson, the government's chief medical officer, said: "Most worrying is that over recent years more and more children and young people have been starting to smoke.

Simon Clark of smoking rights group Forest: "We should discourage children from smoking"

"I hope these figures show this trend beginning to change. We must ensure that this decrease is sustained and is not just a short term fluctuation and will need to remain vigilant."

Amanda Sandford of Action on Smoking and Health said it was good news that the proportion of teenagers smoking had dropped, but it was too early to tell if it was a downward trend.

Amanda Sandford: "Good news, but no time for complacency"

"The fact is that teenagers are still taking up smoking in large numbers and we cannot become complacent," she said.

The figures also showed that although many teenagers who smoked remembered health education lessons, they had chosen to ignore them.

"The government must keep up the good work, but it must also keep its policies under constant review to make sure the message gets across," Ms Sandford said.

Amanda Sandford of ASH: "Raising the legal age is a difficult issue"

Roger Howard, chairman of the Standing Conference on Drug Abuse charity, said there should be more education on the connections between drinking, smoking and drugs.

"It is very worrying to see that four per cent of pupils had been offered heroin," he said.