Children should not drink alcohol before the age of 15, according to England's Chief Medical Officer.
In a five-point guidance published today, Sir Liam Donaldson said for young people not drinking is "the healthiest option" and accused parents of a "laissez-faire" approach.
The guidance says if 15-17 year-olds drink alcohol, "it should always be with the guidance of a parent or carer or in a supervised environment".
The guidance follows a draft proposal in January and the government said the majority of parents welcomed the clear guidelines.
It is the first time advice on children and alcohol has been set out for parents.
And it will be the basis of a new national campaign to be launched by the Department for Children Schools and Families in the New Year.
Sir Liam, who announced this week he would be retiring in May, said: "Across England, half a million children between the ages of 11 and 15 years will have been drunk in the past four weeks.
"The science is clear. Drinking particularly at a young age, a lack of parental supervision, exposing children to drink-fuelled events and failing to engage with them as they grow up are the root causes from which our country's serious alcohol problem has developed."
Chris Sorek, chief executive of charity Drinkaware said the guidance was "extremely useful".
"It's imperative that from an early age, we start to educate children and young people about the dangers of alcohol misuse," he said.
Donaldson also renewed calls for minimum pricing of alcohol - and he said he would keep pushing for the measure even after he has left his post.