London - Children under two should not be allowed to watch screens, UN experts said.
They warned that even a minute a day in front of the TV or playing on tablets and smartphones could be dangerous.
The guidelines – the first of their kind for toddlers – highlight the risk of obesity and of educational problems. Pre-schoolers glued to screens take longer to learn words, are worse at counting and have shorter attention spans.
After assessing hundreds of studies, the World Health Organisation experts said that under-fives should have no more than an hour a day of screen time. They advised a total ban for the under-twos.
John Reilly, a University of Strathclyde professor who helped draw up the guidelines, said strong evidence showed that screens were harmful for very young children.
He added: "Experts have been criticised for trying to turn back the clock by keeping young children away from screens, but you do not have to go too far back to see that they used to play quite happily without screens and not get bored."
The new guidance sets out recommendations
On screen time, sleep and physical activity for children under one, aged one to two and three to four. Its report states: "For one-year-olds, sedentary screen time is not recommended. When sedentary, engaging in reading and storytelling with a caregiver is encouraged."
Screens themselves – rather than simply sitting still – appear to be the problem, as time spent in front of them was linked to problems with cognitive development.
Professor Reilly added: "We adopted the recommendation of no screen time for children under two because the earlier the age, the more potentially harmful it is.
"Their brains are still developing at this age and watching a tablet tends to displace vital activities like sleeping, interacting or being read a story.
"The use of time is very important for a child’s development milestones, and passively looking at a screen does very little to stimulate them or help them learn."
However some experts expressed caution. Dr Max Davie, of the Royal College of Paediatrics and Child Health, said: "We welcome the WHO’s focus on these important health issues and hope that this attention can lead to more research and interventions to help children and families live healthy lives.
"However, recommendations alone can have a number of unintended consequences, and simply proposing standards without providing the right support could discourage families rather than motivate."
Professor Andrew Przybylski, of the University of Oxford, said: "None would contest the fact that increasing physical activity, sleep and health are important goals and it is possible that screens impact young people in a wide range of ways but we won’t know that until good scientific studies are done."
The report also recommends under-twos should get three hours of physical activity a day and 11 to 14 hours of sleep.Daily Mail