A pair of swans are facing execution for putting pilots in danger by straying across a flight path.

Wildlife campaigners are outraged by the "shoot-to-kill" licence given to Shoreham airport.

They have vowed to protect the birds, nesting near the runway, by moving them to a safer place.

However, the swans' nesting ground is on Sibella Pannell's five-acre property off Old Salts Farm Road in Lancing, west of the airport and she is refusing to allow anyone on her land.

She says they are a mating pair and have a right to stay.

A licence to cull the swans has been granted by the Department of Environment, Food and Rural Affairs (Defra).

It is only a matter of time before the airport's pest control team shoots the birds, which it has permission to do if the birds fly across airport land.

The birds have had a number of near-misses with planes and airport managers begged for permission to remove them.

Mrs Pannell's land is a nesting ground for a host of wild birds and ducks, all of which may stray across flight paths at times.

She said her four children and seven grandchildren enjoyed watching the array of wildlife in her garden and was furious the two swans had been singled out for slaughter for the sake of recreational aircraft.

Mrs Pannell said: "I am really angry. If the swans fly from the River Adur to here that is their right.

"Why should they be moved just because the airport wants them moved?

"Swans are together for life, they have a mate for life. It would be terrible if one got shot."

Airport manager John Haffenden said it was vital to get rid of the swans to prevent any catastrophic mid-air collisions.

He said: "The airport, although required under its airport licence to take this action to ensure airport safety, is reluctant to if there is an alternative."

Airport staff approached the RSPCA for advice.

The RSPCA suggested taking the birds to a sanctuary but Mrs Pannell refused to allow inspectors on her land because she did not want the swans moved.

RSPCA spokeswoman Klare Kennett said: "We only have permission to remove the swans if we get permission from the landowners to do so.

"We can understand but the landowners are not going to enjoy the sight of a swan being hit by a plane or a plane being hit by a swan.

"These swans are flying over Shoreham airport every day and could cause serious accident or loss of life."

It is widely believed that all swans in England belong to the Queen but she actually only has the rights to those on certain tributaries of the Thames.

A licence from Defra and permission from the Royal Swan Marker is needed to kill any swans.

Defra officials gave permission for up to two swans to be shot if they were seen flying along the hard runway and were a danger to aircraft.

A spokesman said: "Swans can potentially be owned by the Crown but Defra does discuss all such licences with the Royal Swan Marker and did so on this occasion.

"It is not easy to persuade them to go elsewhere. A bird-scaring regime is in place on the airfield but is ineffective against these swans.

"The birds fly over the airfield as a direct route to the river and unfortunately shooting may be necessary as a last resort."

Dorothy Beeson, of the National Swan Sanctuary, was disgusted that a shoot-to-kill licence was granted but wanted to resolve the matter by offering Mrs Pannell two disabled swans if she allowed the endangered ones to be removed.