A research team at Bath and Bristol Universities studied 5,500 youngsters and found that fewer than three per cent of 11-year-old children were active enough to stay healthy.
According to researchers, Britain has built "an environment that is toxic" to children being active and energetic.
The findings will spark off concerns about the degree of the couch potato culture, with parents afraid to let children out to play, while youngsters preferring computer games to sport.
Doctors have warned that this generation of overweight, lazy children could be the first to be outlived by its parents, reports the Telegraph.
Sir Derek Wanless, a former adviser to Gordon Brown, carried out an evaluation of the NHS warning that the obesity crisis will devastate the health service.
The findings of the latest study indicate that more than 700,000 children are putting their future health at risk.
The study has been published in Archives of Disease in Childhood.