The average age of children using drugs is said to be dropping

The study into youngsters aged 10 to 12 revealed that a third had been exposed to illegal drugs and one in 20 had used them.

The experts, who questioned children in Glasgow and Newcastle, said the report showed a need for schools to tailor drug education to specific age groups.

They also called for parents to exert a greater degree of supervision.

The researchers, who questioned 2,318 children, found that children who were living in families with a low level of parental supervision were eight times more likely to have started to use illegal drugs than youngsters whose parents exercised a high level of supervision.

We will face the horrifying prospect of increasing numbers of children who have become addicted to illegal drugs before their voices have broken Professor Neil McKeganey

They also found that children living in families where other people were using illegal drugs were seven times more likely than their peers to have become users.

Professor Neil McKeganey, head of the university's Centre for Drug Misuse, said: "This research shows that illegal drug use is occurring at an increasingly young age and that as a result drug prevention is a more important task today than at any time in the past.

"If we fail to meet the needs of these vulnerable young people we will face the horrifying prospect of increasing numbers of children who have become addicted to illegal drugs before their voices have broken."