A fishing club fears for its future because its waters are being choked by the invasive aquatic plant pennywort.
The plant, which can grow at up to 20cm a day, is causing major problems for the Offord and Buckden Angling Society.
Chairman Tony Elliott is worried that members will quit if the plant - which already stretches bank to bank in some places - continues to limit the areas where they can fish.
Members have been pulling the plant, which forms giant floating beds, from the water but have been unable to keep up. A popular pike fishing spot can no longer be used.
Mr Elliott said: “It has been a problem for the last two years, really.
“Three years ago it wasn’t a problem, last year it was a problem and this year it has been a huge problem.”
He said: “At the moment the impact is very worrying because we will lose members if they can’t fish and the situation is getting beyond our control. Ultimately, I can see people not rejoining the club because they can’t get access to the water.”
Mr Elliott said the club’s waters were off the main part of the river used by boaters which meant they were unlikely to get any priority for the removal of the plant.
He persuaded Environment Agency staff to clear their main pool where there had been an estimated 30 tonnes of the plant.
Mr Elliott said the agency had been caught out by the sudden appearance of the rapidly-growing pest and did not have the budget to tackle it.
“I am not blaming the Environment Agency. It is an ever-growing problem but it needs to be addressed,” he said. “They know they have a big problem. We are doing our best but we need a bit of help.”
An Environment Agency spokesman described pennywort as the UK’s most problematic invasive non-native plant species.
“We have been clearing pennywort throughout the summer, targeting places where it could cause a flood risk and protecting the conservation features of the Ouse Washes Site of Special Scientific Interest.
“In the coming weeks our harvesting machines will be out again targeting floating pennywort on the River Cam and Ely Great Ouse which will continue until the end of the year.”
The spokesman said: “We prioritise our work in accordance with our immediate action plan and our longer-term five year plan to eradicate the species.
“We would ask angling clubs who believe they are impacted by the presence of floating pennywort to report sightings to the Environment Agency at Anglianemail@example.com or call the national customer contact centre on 03708 506506. Alternatively, they can seek advice from the local Environment Agency fisheries officer.”