The biggest survey of its kind, conducted by the Department of Health, found that children are not getting the recommended one hour of physical activity outside of school times.
Almost half of children watched TV or played non-active video games before school and only a fifth of children did something active after dinner, the Change4Life survey found.
Over 11m questionnaires were distributed through GP surgeries, letterboxes, websites and magazines. Of the 260,000 responses 72 per cent of families said their children were not getting one hour of physical activity outside of school.
The findings,. of the How Are the Kids survey, were released to coincide with a new advert to encourage activity in children.
One third of children under 16 in England are thought to be overweight or obese and this is projected to rise.