An advocate of grassroots sports facilities today accuses the Culture Secretary of adopting an elitist policy that puts winning Olympic medals ahead of mass participation.

Alison Moore-Gwyn, chief executive of Fields in Trust, said ministers appear to have retreated from the Government's pledge to get two million more people involved in sport.

FIT, formerly known as the National Playing Fields Association, fears sports pitches are still being sold off or built on despite ministers' pledge to boost community sports when they secured the 2012 Games.

"The Beijing medal tally was fantastic and gave a huge boost to the whole nation and, understandably, there is a desire to ensure that this can be matched - or even superseded - by London 2012," Ms Moore-Gwyn said.

"Improving facilities for elite level athletes is vital but hosting the Olympics represents a real chance to promote physical activity to every single person in the country by growing grassroots sporting participation. It is this that should be the resounding legacy of the 2012 Games."

Her comments challenge the Government's stronger focus on top athletes brought in by Culture Secretary Andy Burnham and his predecessor James Purnell. Ms Moore-Gwyn echoes former Sport England chairman Derek Mapp, who told last week how he quit after refusing to support the new policy.

The Evening Standard has launched its 2012 Sports Legacy campaign to ensure that the London Games live up to the pledges made in 2005 to champion "sport for all", particularly among young people.

FIT will later this month begin a campaign to highlight the importance of recreation grounds to communities and to safeguard as many as possible before the London Olympics.

The FIT for Gold project will establish protection for fields nominated by local communities to be protected against developers or sell-offs. Ms Moore-Gwyn said the continuing risk to green spaces cast a shadow over the sporting legacy of the Games, adding that five threats to playing fields are being reported to her organisation each week. However, ministers appear convinced that winning medals for Britain will motivate young people on its own.

"Focussing on the high end of elite participation may help create inspiring stories but it doesn't help much in the longer term to galvanise new sections of the population to get involved in physical activity or to ensure that they have space and facilities to participate," she said.

The most recent Government figures show that there are 17 planning applications to build on playing fields every week . In most cases, ministers say the proposals end up improving sporting facilities because they include floodlights or indoor facilities.

However, FIT says the official figures do not reveal the full extent of the loss of land because small plots are not listed.

Alex Welsh, chief executive of the London Playing Fields Association, said there were no reliable figures, and loopholes existed in the official protection. "This means that playing fields can be lost without ever coming on the radar," he said.