A boy who discovered a swan drowning in a river gate has told of his distress at lack of action by the Environment Agency.

Dane Southgate, 13, has been supported by members of the West Sussex Wildlife Protection Group who confronted the agency, presenting staff with the body of the swan that drowned in a sluice gate at Mill Stream, Arundel.

Simon and Jaine Wild and Jeanette Plimmer staged the protest because they believe the swan could have been saved if the agency had opened the gate. They said managers did not seem to care because it was only a swan.

Dane, who was with his mother Lynn when he spotted the swan, said: "I feel disgusted with the agency because it is cruel to let a bird die like that. It got waterlogged and suffered.

"The swan had got pushed down by the current and was stuck. I couldn't get to it because the gate wasn't open. I felt helpless."

Home-educated Dane and Mrs Southgate called the RSPCA.

The Environment Agency was called but Mrs Southgate said the manager, Tony Davidson, told her the RSPCA was responsible for animal rescue.

The swan paddled desperately for several hours as the tide rose but its efforts were in vain. When examined the next day, evidence of its struggle upset bird lovers. The skin had completely worn away on its webbed feet.

Mrs Southgate, 40, a smallholder of Arundel Road, Fontwell, said: "A grid should be fixed to stop a child falling into the sluice. This comes just over a year after a puppy drowned in a nearby sluice gate on the Arun."

Mr Wild, spokesman for the wildlife group said: "Our view is there is a design fault with the sluice and that once a dog, swan, or even a child enters at low tide, it is doomed due to the water pressure in the tunnel.

Ray Kemp, a spokesman for the Environment Agency, said: "We are completely dedicated to caring for wildlife.

"Many of our staff were very distressed about the death.

"But the gate is gravity-fed. There was no way we could open it under those tidal conditions. The river is one of the fastest-flowing in the country."

He said a safety grid could not be fixed on the sluice, which leads from Swanbourne Lake to the River Arun, because smaller birds and debris would get caught.

RSPCA inspector Tony Pritchard, who tried for two hours to save the swan, has urged the Environment Agency to put a grid across the sluice hole by the rapidly-flowing waterfall, to prevent further accidents.