Hundreds of dead fish have been floating to the surface of Abington Park lake over the past two weeks, but an Environment Agency investigation has so far failed to determine the cause.

Suggested reasons have included pollutants in the water or a lack of oxygen caused either by the hot weather stimulating pondweed growth or by decomposing bread fed to the ducks.

But according to Northampton mum Shirley Holmes, an angler of 16 years, the fish are in fact dying from a deadly contagious disease known as fin rot.

"I have been down to the lake and picked up several fish from the water, and none of them have had fins," said the 40-year-old, of Wellingborough Road, Abington.

"From the evidence I've seen, I'm 100 per cent certain, it is fin rot. It has been an ongoing problem at the lake for a couple of years but I've never seen it as bad as this."

Abington Park lake is stocked with a variety of common fish including bream, carp, perch, roach and tench, of which there are believed to be several thousand in total.

Unusually high numbers have been found dead in the past two weeks and firefighters were even called to the park on Saturday to help with the problem, using a fire engine hose to recycle the water which was thought at the time to be low on oxygen.

Environment Agency tests have since proved there is no oxygen shortage in the water, and spokesman said it was unlikely to be polluted.

But Miss Holmes warned many more fish could die if the fin rot problem was not dealt with soon.

She said: "If it is left unattended it could spread to the whole lake, which would be a terrible shame."

Rita Penman, of the Environment Agency, said the lake would be closely monitored over the coming weeks for further signs of the disease, which is caused by bacterial infection.

"When the weather gets warmer as it has done in the past couple of weeks, there is an increase in bacteria, which can result in fin rot," she said.

"We would advise anglers to remove dead fish from the water as much as they can to minimise the risk of it spreading."