One in three parents do not talk to their children about the dangers of alcohol, making underage drinking the "forgotten factor" threatening young people's safety, according to new research published today.

Only thoughts of their offspring smoking or having weight problems worry parents less than drinking, the survey found, and almost two-thirds did not even think their child would consume alcohol.

Instead, parents of nine- to 16-year-olds are more concerned about unwanted pregnancies, car accidents and drugs.

The children's secretary, Ed Balls, urged parents to warn their children about the dangers associated with drinking alcohol as they gear up to celebrate New Year's Eve.

The plea comes weeks after the chief medical officer, Sir Liam Donaldson, recommended that no young person under the age of 15 should drink at all.

Today's research, by parenting website Mumsnet, found that while the vast majority of parents (97%) feel comfortable discussing alcohol consumption with their children, and more than 90% recognised drinking was harmful to young people, only two-thirds discussed the role alcohol played in issues such as sex, drugs or personal safety.

Balls said: "It is reassuring that parents understand the importance of discussing alcohol with their children, but it is really important that they make the link between alcohol and the impact it can have on a young person's safety.

"Research tells us that young people who regularly drink alcohol are more likely to fall behind in school, be involved in road traffic accidents or have unsafe sex.

"If parents discuss the link between alcohol and these other issues, they can make sure it's their child making the decisions, not the alcohol."

Setting out new guidelines on young people and alcohol earlier this month, Donaldson said parents who give their children watered-down wine in the hope of introducing them to sensible drinking habits are misguided.

There was no evidence to support the notion that children would learn to handle alcohol better if introduced to it at an early age, he explained. Instead, the earlier they were introduced to it the more likely they were to get a taste for it and to end up binge drinking or drinking heavily as adults.

Donaldson advised that 15- to 17-year-olds should be allowed to drink only under parental supervision.

The Mumsnet survey of more than 800 parents showed that only a quarter speak to their children regularly about the risks associated with drinking. Carrie Longton, co-founder of the site, said alcohol and how best to talk to children and teenagers about it was a hot topic.

Comedians Bill Bailey, Russell Kane, Josie Long and Jo Brand are supporting a viral marketing campaign on young people and drink, running until a national advertising campaign is launched next month.