Children should not spend any time looking at phones, tablets or TVs until they are at least two years old, the World Health Organization warned last week.
New guidelines on how much activity children should do have been revealed by the world's highest health authority.
Screen time may lead to children being obese, having slower brain and physical development, and worse mental health, the WHO report suggested.
Instead, it recommended children spend time reading or being read to, doing puzzles, drawing or singing in order to improve their brain development.
The advice will be unwelcome to many British parents – more than half of three to four-year-olds use the internet every week and one in five have their own tablet.
Experts in the UK have not readily accepted the WHO's warnings, being sceptical about the dangers of screen-time and criticising the quality of scientific evidence.
The WHO has published its Guidelines on Physical Activity, Sedentary Behaviour and Sleep for Children Under Five Years of Age. It says babies and one-year-olds should not spend any time at all looking at electronic screens.
Two, three and four-year-olds should be limited to just one hour per day and 'less is better', the report said.
'The benefits of less screen-based sedentary behaviour (TV viewing, watching videos, playing computer games) include reduced [obesity], improved motor and cognitive development and psychosocial health,' the report said.
Experts at the WHO issued the new advice as scientific evidence continues to build of the potential harms of children using screens too often.
Research published earlier this year found pre-school children in the UK spend, on average, an hour and 16 minutes online every day.
Almost one in five (19 per cent) of toddlers have their own tablet, and more than half (52 per cent) go online every week for an average of nine hours.
Under-fives spend two hours per day watching TV on average, while 45 per cent of them use YouTube and nearly a third use video streaming services like Netflix.
However, the WHO's advice, to be presented at the European Congress on Obesity in Glasgow, has been met with criticism from British experts.
There are concerns the evidence the recommendations are based on is of too low quality – something the WHO itself acknowledged.
And critics say proof of the harms of screen-time are not established enough to warrant firm guidelines.
