Save Radley Lakes campaigners descended on the home of RWE npower at Didcot power station and handed in an 11,500-named petition with the message: "Hands off Radley Lakes."

But power station manager John Rainford issued an equally direct response when he told a delegation headed by Oxford West and Abingdon MP Evan Harris that there was no alternative but to dump spent fuel ash in Thrupp lake.

Mr Rainford warned: "If we do not have this facility then we will not be able to operate at full capacity. We could not guarantee security of supply."

A coachload of more than 50 people turned up at the power station to protest at npower's plans to pump millions of tonnes of spent fuel ash into the old gravel pit lake at Radley.

The company's application will be considered by the county council's planning and regulation committee on Monday.

For the last 12 months the Save Radley Lakes (SRL) campaign has been mounting a campaign to thwart the proposals. The group argues that a valuable amenity will be lost and flora and fauna sacrificed.

SRL has been canvassing support from all over Oxfordshire and has drawn up detailed documents outlining alternative schemes npower could explore in place of its ash dumping proposal.

Dressed up as a water vole, Eleanor Dangerfield said: "I and hundreds of other voles are worried about the threat to our homes in the lake and we hope that npower won't evict us and all the other wildlife and plants. We are getting frightened because we don't want our homes ruined by horrible old fuel ash."

Dr Harris said: "Save Radley Lakes has done some very carefully researched work proposing alternatives that the county's planning committee will have to consider. RWE npower must give proper consideration to all the issues and alternatives being proposed to protect this very much-loved amenity."

In a meeting with the delegation, Mr Rainford said the company would take into consideration the petition but said it had already responded to many concerns.