The education secretary has outlined plans to tighten the rules governing the sale of school playing fields.

Charles Clarke announced on Friday that previous Labour legislation will be strengthened by a new set of guidelines.

Successive governments have faced criticism for allowing sales to take place while obesity has risen among young people and participation in competitive sports has declined.

With British sporting success at the Olympic Games currently top of the news agenda, Clarke said he would safeguard facilities for future generations.

The Cabinet minister made clear that the law requiring the proceeds of any sale to be put towards improved PE facilities will be reinforced.

Local authorities will have to prove that they have exhausted all other options for raising revenue before the secretary of state will grant approval for a sale.

A new emphasis will also be put on outdoor facilities in a bid to stop pitches being sold in order to build sports halls.

Instead the education department may grant permissions for "unused portions of playing fields" to upgrade other open air areas with equipment such as floodlighting.

Long term

Councils will also have to prove that new facilities will be used for at least 10 years.

Clarke said he wanted to lock in investment in sport for the long term and won the support of the National Playing Fields Association (NPFA).

"We have already stemmed the tide of playing field sales that took place before 1998, and I am grateful for the support of the NPFA in further strengthening our guidelines," he said.

"This means that school playing fields will now not only be protected but also improved for the benefit of pupils and the wider community.

"It should also challenge the misconception that school playing fields have been sold off indiscriminately.

"We are committed to encouraging the highest quality sport and PE in schools. Over £1 billion has been invested since 1997 to develop school sport, and we are opening 400 specialist sports colleges and school sport partnerships to nurture the athletes of tomorrow."