A ban on homeowners having cats is being proposed amid fears the pets could pose a threat to rare birds.
Cats could pose a threat to the heathland's Dartford warblers
Developer George Wimpey has suggested the ban in an attempt to win approval for a 27-apartment scheme in Berkshire.
The site of the development, in Crowthorne, lies close to the Thames Basin Heaths area, a protected home to rare ground-nesting birds.
The developer has vowed to legally bind homebuyers to the ban but English Nature still objects to the scheme.
The conservationists believe the scheme would have an adverse impact on the heathland, which is a Special Protection Area (SPA) under EU law.
It is home to endangered nightjars, woodlarks and Dartford warblers, to which cats can pose a particular threat as they nest on the ground.
An English Nature spokesperson said: "Cats are only an issue on residential developments 400m or less from the SPA.
"The Wimpey development is, at its closest, 1.2km away so cats aren't a significant part of the disturbance threat on the SPA in this case so Wimpey offering to ditch cats isn't moving us forward at all."
The developers were refused planning permission last year but an appeal is due to be heard.
A spokeswoman for George Wimpey told the BBC News website that the suggested ban was a "genuine attempt" to find a solution to conservationists' concerns.
"One of our thoughts was that if we had a covenant in that said no cats, that would make the situation work and sort this problem out," she said.