A tiny proportion of children are getting the recommended amount of daily exercise, researchers have said.
According to experts at the University of Bath, 95 per cent of boys and 99.6 per cent of girls do not achieve the national target of one hour of physical exercise per day.
The study, which involved 5,595 children, measured children's exercise for seven days and found that the average youngster did just 17 minutes of moderate exercise and two minutes of vigorous exercise per day.
The findings raise concerns about the health of the nation's children and suggest that a growing number may need obesity treatment in the future.
Study authors said that the fact that children's activity levels decline during adolescence was "sobering".
"These children may be predisposed to the development of childhood obesity, the early onset of cardiovascular risk factors and ultimately chronic disease," they claimed in the Archives of Disease in Childhood.
Independent advice on private healthcare