Residents have reacted with horror after an area of outstanding natural beauty was “cut out” of the planned South Downs National Park.

People living around Green Ridge, a thin band of meadowland between the Westdene area of Brighton and the A27, have launched a campaign to urge officials to change the boundary.

All areas inside the national park, which is due to come into operation next year, will be protected against future development.

Those excluded will have no such protection.

Hailey Sellins, whose home backs onto the Green Ridge AONB, said: "Ever since the national park was first considered in 2001 that area has been in it. It has been in every draft until all of a sudden now it is dropped at the eleventh hour.

"We are all horrified. We've had no chance to protest or make a case because there has never been a need."

The residents led by Maureen Holt have now formed a group called Keep The Ridge Green and are lobbying the Department for Environment, Food and Rural Affairs for the boundary to be re-altered.

Mrs Sellins said: "It is an absolutely beautiful area up there and it is used by a lot of people for walking. It is a meadow with a lot of butterflies and other wildlife. David Bellamy went to visit it when he was in Brighton last year. It would be awful if it was lost."

Their cause has been backed by Brighton Pavilion MP David Lepper and Brighton and Hove City Council, which is expected to pass a resolution tonight to write to Environment Secretary Hilary Benn.

Mr Lepper said: "Local people in the area have worked hard to conserve and protect this unique piece of the South Downs. We hope the secretary of state will think again before a final decision is made."

In a report on the issue that will be reviewed by Councillor Geoffrey Theobald, Brighton and Hove City Council's cabinet member for environment, council officers suggest the situation needs to be drawn to Mr Benn's attention urgently and raise the possibility Green Ridge was cut from the park by a clerical error.

They suggest the area may have been accidentally removed at the same time as Toads' Hole Valley, between Hangleton and the A27.

They add that Green Ridge met all the necessary criteria for being included in the national park.