According to official figures, 39% of 15 year olds had used illegal drugs in the past year.

This is higher than drug use among an older age group - 16 to 24 year olds - among which 28% had used drugs in the past year.

This suggests that widespread use of drugs - most usually cannabis - rises most sharply in the middle teenage years.

Among 11 year olds, the figure for drug use is 6%.

There has been no increase in drug abuse among 16 to 24 year olds

And as an average, one fifth of 11 to 15 year olds had used drugs in the course of the year - and 12% had used drugs in the past month.

The figures, from research and surveys in 2001, were from the Government Statistical Survey.

There were also indications that 4% of the age group had tried hard drugs such as heroin and cocaine.

School drug abuse

But figures looking at a wider age group - 16 to 24 year olds - found no increase in drug use compared to successive surveys between 1994 and 2000.

The scale of drug use among school-age youngsters has been previously highlighted by teachers' unions

One in five schools in England and Wales has to deal with cases of illegal drug abuse among pupils each year, a survey from the National Union of Teachers has reported .

Drug dealing was identified in one in seven schools, but this tended to extend "beyond the school gates" or involved parents rather than pupils.