As the rules on outdoor space schools have to provide change, five-time Olympic Champion Sir Steve Redgrave tells Channel 4 News "we need as much space as possible within school areas".
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The Department for Education (DfE) confirmed that a requirement for secondary schools in England to provide pitches ranging from 5,000 sq metres to 54,000 sq metres, depending on the number of pupils, had been dropped.
Instead, under new regulations laid in Parliament last month, schools will now simply have to provide "suitable outdoor space" for PE and for pupils to play outside.
The DfE said that removing "pages and pages" of bureaucratic regulations would make it easier and cheaper to provide the extra places for pupils the country needs but insisited "extremely strict rules on playing fields will stay firmly in place".
Campaigners warned that the move could undermine the future provision of schools sports at a time when the country is looking to build on the success of Team GB in the London Olympics.
Five-time Olympic rowing champion Sir Steve Redgrave told Channel 4 News schools should have "as much space as possible" for children to take part in physical activity.
He also emphasised the importance of time and teacher training: "We're in a society that's safety driven. When I was a kid I could climb trees, roam the streets and kick a ball around. That doesn't seem to be acceptable anymore so more time should be given in the curriculum so children can be active."
Read more: Concerns about securing an Olympic legacy
Tim Lamb, the chief executive of the Sport and Recreation Alliance, an umbrella organisation for sports bodies, told The Guardian that the old regulations had been a "key tool" in preventing playing fields being sold.
"Without a minimum requirement, the danger is that short-term expediency could jeopardise the ability of schools to deliver sport for future generations," he said.
"We're confident that the Education Funding Agency understands the need to require schools to retain a minimum playing field space because the previous requirements were one of the key tools for preventing the sale of land."
The DfE said that at some point over the next 12 months it would be publishing guidance with a formula setting out the minimum outside space schools would have to provide - although it had yet to consult on it.
A spokesman said: "These regulations set out for the first time that all schools must have access to suitable outdoor space for both formal PE lessons and for outdoor play.
"By removing pages and pages of bureaucratic restrictions we will make it easier and cheaper to provide the extra school places that this country needs so urgently.
"Our extremely strict rules on playing fields will stay firmly in place. This government has only approved sales if the school has closed, has merged or if equal or better facilities are being put in their place.
"We will be consulting later this year on how the new guidelines should be implemented."
It is understood that the previous Labour government approved the sell off of more than 200 playing fields over 13 years.
And an estimated 10,000 were disposed of between 1979 and 1997.
13 August 2012