Nearly one million children are not receiving at least two hours of exercise at school a week, the government has admitted.
A written answer by schools minister Kevin Brennan stated that 900,000 children were not receiving this level of physical activity in school, prompting criticism from the Conservative party.
The 2004 comprehensive spending review's public service agreement requires 85 per cent of five- to 16-year-olds to have at least two hours of high-quality PE and school sport by September 2008.
Mr Brennan said the 2006/07 school survey showed 86 per cent were doing the two hours, but shadow sports minister Hugh Robertson responded to the news by suggesting rising obesity levels were "hardly surprising" in this context.
"Instead of announcing unbelievable targets with inadequate resources and no delivery plan, the government ought to be concentrating on reaching the one million children that a decade of Labour government has so conspicuously failed to reach," he said.
Mr Brennan said he expects the number of children not receiving their two hours' weekly exercise at school to drop "significantly" by September 2008. The government has already made substantial progress, having raised the two-hour percentage from 25 per cent in 2002.
It hopes that ending the 'no ball games' culture will improve the situation, having announced plans to invest £30 million in enabling sports colleges to upgrade their facilities so they can be used "all year and around the clock".
Children, schools and families secretary Ed Balls said he wants to see parks, playgrounds, basketball and tennis courts opened for longer hours to create new exercise opportunities.
"We want to encourage everyone to take part in sport - and making sport an attractive option for all young people is especially important if we are to tackle obesity and give young people enjoyable and positive activities they can take part in after hours," he said.