Campaigners trying to prevent a lake at Radley being used to dump spent ash from Didcot power station have lost another battle in their fight.

Six months after granting planning permission, Oxfordshire County Council has finally issued approval for the former gravel pit at Radley to be filled with half-a-million tons of pulverised fuel ash from Didcot until 2015.

But objectors believe they have another ace up their sleeves - getting Village Green status for the area. The move follows a successful bid which thwarted Oxford City Council plans to build houses on the Trap Grounds in North Oxford.

The power station plans to pump fuel ash via an existing pipeline from Didcot to the lake. The site would then be restored as a wildlife reserve.

The planning permission includes 36 conditions, controlling issues such as protection of ecology, minimisation of disturbance to users of rights of way and prevention of flooding.

There is also a legal agreement to ensure that certain other areas at Radley are not used for the disposal of ash from Didcot in the future, and for the long-term management of the site.

Despite a vigorous campaign mounted by Save Radley Lakes, a petition with more than 11,000 signatures and 3,000 letters of objection, the county council granted planning approval last summer.

Objectors asked the Secretary of State for Communities and Local Government, Ruth Kelly, to intervene but she declined to get involved.

The council says there are no grounds for further delaying permission.

Sustainable development unit head Chris Cousins said the county council had a responsibility to local interests, consultees and the applicant. Organisations such as English Nature and the Environment Agency had not objected to the development.

But campaigners have not given up the fight. Save Radley Lakes member Jo Cartmell, from Abingdon, submitted an application to have an area at Radley lakes registered as a Village Green.

If the Village Green application is successful and Village Green rights are found to exist, it would be the responsibility of Didcot power station owners RWE npower, as landowner, to respect the rights.

Mr Cousins said: "The Village Green application and the planning application are governed by different legislation and the council has to treat them separately.

"We have, nevertheless, in issuing the planning permission, made sure that we advised RWE npower of their potential responsibilities should the Village Green application be ultimately successful. "

Campaign group chairman Dr Basil Crowley said: "The council's decision to grant planning permission is a blow to us - but we are not throwing in the towel.

"We want to see the area granted Village Green status to protect the whole area and we are calling on npower to consider other options.

Dr Crowley added: "Once Thrupp Lake is filled with fuel ash it will take a very long time before it is restored for wildlife."