CAMPAIGNERS want to derail plans for 500 homes in Bicester by having the land designated as a nature reserve.
They say the move would scupper Gallagher Estates’ plans for land at Gavray Drive, one of the last green spaces inside the ring-road.
It won permission from Cherwell District Council in 2006, renewed in 2011, but that was quashed by the High Court in January.
Ecologist Dominic Woodfield said the council failed to comply with environmental impact assessment regulations.
Mr Woodfield said Gallagher had “grossly under-played the ecological importance of the site”.
A new plan has not been submitted and the developer declined to comment.
Campaigners say the land is teeming with wildlife such as rare butterflies, flowers and great crested newts.
Bicester Green Gym, Grassroots Bicester and Langford Community Orchard Group have joined forces.
Dr Pam Roberts, from the campaign, said: “It has got tremendous value intrinsically as a ecological site, and terrific value to Bicester as breathing space, because Bicester is short of open space. She said: It’s the last segment of Bicester that hasn’t been built on.
“Gavray Meadows are full of wonderful flowers, it’s quite amazing, and supports a whole network of butterflies and wildlife.
“We need to preserve it for education and for future generations.
Campaigners say other planned estates like at Graven Hill and the north west eco town will meet demand for homes.
More than 160 people have signed a petition calling for the land to be used as a nature reserve.
Dr Pat Clissold, of the Thames Valley Environmental Records Centre, said she has seen rare butterflies and snakes and lizards.
The black and brown hairstreak butterflies and great crested newts are protected under European law.
The retired scientist said: “To all intents and purposes it’s just a boring old field because no-one has been over there and said they saw this or that.”
Berkshire, Buckinghamshire and Oxfordshire Wildlife Trust (BBOWT) has recognised the land as a wildlife site.
Head of conservation and education Neil Clennell said: “The fragments which are left, such as Gavray Drive Meadows, are highly valuable both as a rare habitat, and in providing a home for threatened species.
“Pockets of natural habitat provide important links that allow wildlife to move across the landscape, adapting to changes in the environment such as climate change.”
The land is divided by Langford Brook and an areawill be used for a new railway line.
It is part of Chiltern Railway’s Evergreen Three scheme, linking Bicester Town and Bicester North Stations.
Some 5,000 homes are planned for the eco town with 2,300 homes at Kingsmere and up 1,900 at Graven Hill.
The district council was not available for comment.
For information search for Save Gavray Wildlife Meadows For Bicester on Facebook.