Figures put together by the National Playing Fields Association show the number of school and community sports pitches in England has fallen from almost 78,000 in 1992 to 44,000 today, strengthening fears that children are not getting enough opportunity to exercise.
While most were lost under the Tories, almost one a day has gone during the eight years of the Labour Government, despite a manifesto promise in 1997 to halt the sale of school playing fields.
Don Earley, the association's deputy director, said although the Government had tightened regulations on selling off sports facilities for development, pitches were still disappearing. "We have lost a lot of space, which was used not only for educational purposes but also informally by children, and this comes when there is concern about children's health and activity levels," he said.
An audit by the now defunct Sports Council revealed that in 1992 there were 77,949 pitches at 25,940 sites in England. According to the Department of Culture, Media and Sport there are now 44,000 pitches at 21,000 sites, a loss of almost 34,000 pitches, 45 per cent of the total.
Some of the pitches had been replaced with indoor facilities, but Mr Earley said that the balance had tipped too far away from outdoor sites.
He said: "We do not have a problem with indoor facilities but I do not think it should be one or the other. We should have both because they perform different functions. We are seeing the disposal of outdoor pitches to fund indoor sport, and I think that sort of balance is not healthy."
But a DCMS spokeswoman said the 44,000 referred only to outdoor football pitches, and an audit of fields used for other sports was under way and would be completed by the autumn.
Richard Caborn, the sports minister, said the latest figures show 72 playing fields created in 2003-4 and 52 lost, a net gain of 20.
He said: "More playing fields are being created or improved than are being lost and this shows that we are starting to turn the tide on the playing field issue."