Children with a TV in their bedroom watch an extra 15 minutes a day compared to those without, experts have said.
A study of 12 to 15-year-olds found having a TV pushed up overall viewing time, while parents who watched a lot of TV tended to have children who watched more.
More than 1,200 children were included in the research, published in the International Journal of Pediatric Obesity.
Overall, girls watched more television but boys were more likely to have a TV in their bedroom.
Around four in 10 youngsters in the overall group watched TV for two hours or more per day.
Health experts said the findings had implications for the future health of British children. Excessive TV watching and a lack of exercise have both been linked to obesity.
Johannes Brug, lead researcher for the study from the VU University Medical Centre in Amsterdam, said: “Our research suggests that factors in the home have an important effect on how much time adolescents spend watching television.
“We now need to do further research to see whether making changes in the home environment by, for instance, taking televisions out of adolescents’ bedrooms or introducing rules on television viewing, reduces viewing time.”
In the study, the researchers said parents had a lot of influence.
“As parents mainly shape the home environment for adolescents, parents should be targeted,” they added.
Panagiota Mitrou, deputy head of science for the World Cancer Research Fund, which part-funded the study, said: “There is now very strong evidence that it is important to get children into healthy habits as early as possible in life and limiting the amount of television they watch is part of that.
“This study suggests parents can play an important role in making this happen by setting a good example themselves and by not allowing their children to have a television in their room.
“If children watch less television then they are less likely to grow up to be overweight, which is important for reducing their risk of cancer and other chronic diseases.
“Television viewing reduces the amount of time available to be physically active, and people use even fewer calories while watching television than when reading a book or sitting and talking.