Airport operator BAA is facing opposition to its plans to route a new rail link to Heathrow across common land.

The proposed Heathrow Airtrack would connect to Terminal Five from the South and West, but plans to construct the railway across Staines Moor are being resisted by the Open Spaces Society. The land lies north of Staines in Surrey.

Spelthorne Borough Council describes the moor as “One of the remaining Commons of the mediaeval Manor of Staines.

“Originally a clearing in the Forest of Windsor it has remained unploughed for over 1,000 years. The moor has been registered common land since 1065 and only registered commoners are entitled to graze their animals on it

“By Act of Parliament, common land also provides the public use of the land for ‘air and exercise’. The 289 acres [117ha] is under constant threat from developers and gravel raisers even though much of it is a designated Site of Special Scientific Interest.”

BAA issued three alternative routes for the new track, but all encroach on Staines Moor.

Kate Ashbrook, general secretary of the OSS, said: “Staines Moor is of exceptional value to the public and it would be an outrage if it were to be devastated by the proposed railway.

“The moor dates back to medieaval times and is a unique area of open country sandwiched between the M25 motorway and the Staines reservoirs, on the edge of conurbations. It is an oasis and a refuge for people and for wildlife.

“Because this is common land, it may only be used for another purpose if equally advantageous land is provided in exchange. Obviously this is impossible. There is only one Staines Moor.”

BAA says it has altered its plans to reduce impact on the environment. It said: “Overhead line electrification will not extend onto Staines Moor. The route of the line across Staines Moor has been moved closer towards the M25.

“The route chosen will minimise impacts on the open space of Staines Moor, as well as on the marshy area to the west, both of which are within the SSSI.

“Protection of the environment has been and will continue to be one of the most important aims in developing the scheme. We have tried to avoid impacts on the environment wherever possible and to minimise any adverse effects.

“The choice of route will ensure impacts on Staines Moor’s historic and cultural significance are minimised. Our archaeologists are working to identify where buried remains may be at risk. They will agree with local councils the need for and scope of more detailed investigations prior to construction.”

However, Ms Ashbrook said: “No other land will have the history or the well established habitat, flora and fauna of Staines Moor. It is irreplaceable.”

“So we have called on BAA to abandon its plans to route the Airtrack railway over the moor and to think again.”

If the airport company’s plans are approved, building on the route is due to start by the end of next year, with trains running in 2014. A public inquiry is expected later this year.