People should take steps to protect areas of green space that they have used informally for years - before developers try to exploit them, conservationists urged.

The Henley-based Open Spaces Society said that many communities took their green spaces for granted, only to find it difficult and expensive to get them protected once they were threatened by development. But if land had been used by residents for informal recreation for 20 years they could register it with local authorities as a green space, affording it legal protection from “encroachment” under 19th-century laws. It was a process much easier to achieve if the land was not already earmarked for development, said Kate Ashbrook, the society’s general secretary.

Once developers were interested in land they could put financial and legal resources into opposing bids to register the place, Ms Ashbrook said.

She cited Croxley Green in Hertfordshire, where it took four years and a public inquiry to save their green space from development. She also said the Cloffocks in Workington, Cumbria - where a traditional Easter game of “Uppies and Downies” has been played for centuries - has not been registered and campaigners are now fighting plans for a Tesco supermarket on the site.

On the type of open space that could be registered, she said: “It could be land behind a housing estate. It’s not going to be your traditional bit of village green but could be somewhere the kids have always used.”

She said people took that kind of land for granted and then were shocked when development plans were drawn up for it.

Writing in the society’s magazine, Open Space, she said: “Parish and community councils and other local groups should set up a task force to seek out and map those bits of land which local residents cherish.

“With good evidence of use and the Open Spaces Society’s help, they can get them registered as greens now.

“That will thwart future developers and secure the space for all time.”

She added that since the law on protecting village greens was clarified last April, the number of queries the society had received on how to register green spaces had doubled.

Times recommends

• Energy-saving ideas from switched-on professor
• Rooks are as clever with tools as chimpanzees
• Burping of the lambs blows roast off menu