Heavily oiled oceanic birds being washed up dead on a Jurassic Coast beach are the worst a Purbeck marine photographer has ever seen.

Naturalist Steve Trewhella helped rescue oiled birds from the Napoli disaster, the cargo ship which broke up after being beached at Branscombe, Devon in January 2007.

“Even after dealing with the Napoli I have never seen birds as heavily oiled as this,” he said.

“It’s like they have been dipped, like a toffee apple. Every millimetre of the bird is covered.”

He made the gruesome discovery at Chesil Cove on Sunday when he found two oiled gannets on the beach. One of the stricken birds was completely covered in the thick, sticky oil.

Returning the next day he found 10 more dead birds, fulmar and guillemot among them and the stinking glutinous mess spread along pebbles on the beach.

“It’s probably where someone has dumped oil at sea,” he said.

“A ship has flushed its tanks out or had oil they didn’t need and just dumped it.

“I don’t think there’s an oil spill. There would be a lot more oil on the beach,” he said.

The oceanic birds could have encountered the oil far out to sea, diving into it or it trapping them with its sticky coating on the surface. One gannet had been ringed on Guernsey.

“Generally speaking they pair for life and go back to the same nesting colony,” he said.

But it is not just large birds that will perish. Creatures which inhabit beach strandline are also at risk, including the scaly cricket, which is one of Britain’s rarest insects.

And if the wind continues to blow in the same direction, he fears there may be many more dead birds washed up in the days to come.

The RSPB has urged anyone who finds any live oiled birds to contact the RSPCA immediately