British children are among the least active in the world, and fitness levels are plummeting, an international study has warned.
Experts said the results were alarming, showing that movement was being "stripped out" of modern lifestyles, with children weaned on screen-time and starved of outdoor activity.
Research comparing the activity levels of children in 38 countries across the world put England, Wales and Scotland behind countries like Ireland, Slovenia and the United Arab Emirates.
On Sunday night Simon Stevens, head of the NHS, called for radical changes in family routines, describing exercise as a "magic pill" which would be a "pharmaceutical blockbuster" if only it could be bottled.
Although the UK government recommends children should do at least an hour of moderate intensity physical activity just 15 percent of girls and 22 percent of boys aged 11 to 15 in England managed this.
The report shows that the fitness of children in England has deteriorated badly since the first such global research was published two years ago, despite repeated pledges by the Government to tackle childhood obesity and couch potato lifestyles.
In 2014, England was given an overall grade of C-D, in the first Global Matrix of Grades examining fitness. Since then, of nine different measures used to rank activity levels and government strategies, four have worsened while the rest are unchanged, bringing its overall grade down to D minus.
Latest figures show childhood obesity has reached record levels, with one in 10 children obese when they start primary school, and one in five reaching that level by the end of it.