THE more television toddlers watch, the more they are likely to be obese and do badly at school when they are older, according to new research.
Scientists also found such children were more likely to be bullied by classmates and to become obese, as they had a tendency to snack more.
A study of 1,314 children aged 29 months quizzed parents on their children's weekly television exposure.
Researchers found, by the age of nine, those who had watched television the most had more problems in school and poorer health.
The study examined parent and teacher reports of the children's academic, psychosocial and health behaviours as well as their body mass index (BMI) .
Each additional hour of television in early childhood corresponded to a 7 per cent decrease in classroom engagement, 6 per cent decrease in achievement in maths and a 10 per cent increase in victimisation by classmates.
The study also revealed the children did less physical activity, had a higher consumption of fizzy drinks and snacks and a 5 per cent increase in BMI.
The study was conducted by Canadian scientists at the Universit de Montral, the Sainte-Justine University Hospital Research Centre and the University of Michigan and was published in the Archives of Paediatrics and Adolescent Medicine.
Edinburgh-based Sue Palmer, child development expert and author of Toxic Childhood, said: "This is why the French have banned broadcasting aimed at children under three.
"The Australian government has said children under two should not watch television at all and the American Academy of Paediatrics has had that advice for a long time.
"For children who watch television from an early age it becomes a default activity and they aren't learning how to explore their environment."
In 2008 a report revealed Scotland was the second fattest nation in the developed world, behind only the United States. The Scottish Government has since passed legislation banning sweets, sugary drinks and fatty meals from schools.
Dr Linda Pagani, a psychosociology professor at the Universit de Montral, who led the study, said the findings made a "compelling" public health argument against excessive TV viewing in early childhood.
"This is a critical period for brain development and formation of behaviour.
"High levels of TV consumption during this period can lead to future unhealthy habits.
"Although we expected the impact of early TV viewing to disappear after seven-and-a-half years of childhood, the fact that negative outcomes remained is quite daunting."