Children as young as four are being referred to specialist drug and alcohol treatment services in parts of the UK, shock figures have revealed.
Hundreds of primary school children are at risk of becoming addicts, prompting charities to call on the government to improve substance abuse education in schools.
Freedom of Information requests from the Press Association to councils in England, Wales, Scotland and Northern Ireland uncovered data showing young children were being treated for drug and alcohol misuse.
In South Ayrshire, children aged four were referred to specialists. Waltham Forest in east London and East Ayrshire councils referred eight-year-olds, while Herefordshire, Liverpool, Oxfordshire, West Berkshire, Rutland and the Scottish Borders have all seen nine-year-old children referred for treatment.
In Bury, Calderdale, Hull, Monmouthshire and Rochdale, councils have referred 10-year-olds.
A referral indicates that the child is vulnerable to alcohol or drug misuse through exposure to a parent or relative or may have started abusing substances of their own accord.
Experts said the most common way children came into contact with drugs and alcohol was through their parents.
Public Health England statistics show that 366 children aged 12 or under were referred for treatment in 2012 and 2013. Half of those aged under 13 were treated for cannabis misuse and a third were referred for alcohol abuse.
Andrew Brown, director of programmes at the charity Mentor UK, which seeks to protect children from drug and alcohol misuse, said it: "It is vital that alcohol and drug education improve."
He added that the frequency of sessions in schools needed to be increased, as the norm is generally one or two lessons per year.
"This may sound sufficient but evidence would suggest that longer programmes that systematically build skills and values are much more likely to prevent young people from coming to harm than one-off lessons," he said.
Under the national curriculum, schools are required to teach about the harmful effects of drugs and alcohol on mental and physical health. An alteration to the curriculum, which will be introduced in September, states that pupils aged 10 and 11 must "learn to recognise the impact of diet, exercise and drugs and lifestyle on the way their bodies function".
A government spokeswoman said: "Both the old and the new curriculum are clear that all pupils should be taught about how drugs and other substances can be harmful to the human body.
"Teachers are also free to use their professional judgment to address any specific issues that meet the needs of their pupils through PSHE [Personal Social Health and Economic Education]."