Middle-class parents who let their children have the odd glass of wine or bottle of beer at home when they are in their early teens are doing them more harm than good, a study finds today (THUR).
Many mothers and fathers think that allowing their children to have a supervised drink is a good way of exposing them to alcohol safely and taking away its illicit thrill.
But new research suggests it sends mixed signals that result in them being more likely to abuse alcohol as they enter their core teenage years.
A joint American-Australian study of more than 1,900 12 and 13-year-olds found that those whose parents took such a "harm minimisation" approach were more likely to have experienced "alcohol-related consequences" - such as not being able to stop drinking, getting into fights, or having blackouts - two years later than those whose parents had a "zero-tolerance" strategy.
A year into the study, almost twice as many Australian teenagers (67pc) had drunk alcohol in the presence of an adult than their American counterparts (35pc), reflecting general attitudes in Australia and the US when it comes to supervised underage drinking.
The following year, just over a third (36pc) of the Australians had experienced alcohol-related consequences compared to only a fifth (21pc) of the Americans.
While cultural differences alone could feasibly account for the disparity, the results also found that teens who had been allowed to drink while supervised were more likely to have had such experiences regardless of which country they were from.
The results of the study, conducted by the Centre for Adolescent Health in Melbourne, Australia, and the Social Development Research Group in Seattle, USA, are published today (THUR) in the Journal of Studies on Alcohol and Drugs.
A separate Dutch study of 500 12-to-15-year-olds, also published in the JSAD today, found that it was the amount of alcohol available at home, and not how much parents drank, that determined teenage drinking habits - suggesting parents should keep their drinks cabinets locked.
Dr Barbara McMorris, of Minnesota University, who led the first study, said: "Both studies show that parents matter.
"Despite the fact that peers and friends become important influences as adolescents get older, parents still have a big impact."
She added: "Kids need parents to be parents and not drinking buddies. Adults need to be clear about what messages they are sending. Kids need black and white messages early on.
"Such messages will help reinforce limits as teens get older and opportunities to drink increase."
But Don Shenker, chief executive of Alcohol Concern, said British research suggested a zero-tolerance approach could be counter-productive.
In a questionnaire, school children aged 10 to 15 were asked if their parents had no interest in their drinking, had a zero-tolerance approach, or showed concern.
Those who parents who let them drink but showed concern, and had a "responsible attitude" to drinking, were better protected against excess drinking than the other two groups, he said.