County Hall is being urged to come clean about sites shortlisted for a £100m incinerator, amid claims key decisions have been taken ahead of a council debate.

Oxfordshire county councillors will next week discuss the implications of burning 200,000 tonnes of household waste a year in a plant to create electricity.

But some councillors have expressed anger that they will be debating alternatives to burying waste, with the decision already taken to build a giant incinerator.

The Green Party is demanding the list of proposed sites for an incinerator are made public.

The Oxford Mail reported before Christmas that after a year assessing alternatives to landfill sites, County Hall had decided to go for incineration.

Labour county councillor, Val Smith, said elected representatives were being given no chance to influence a decision costing council tax payers tens of millions.

Green county councillor Craig Simmons said the debate would take place with some councillors kept in the dark because of "commercial sensitivity."

But Roger Belson, council cabinet member of sustainable development, said: "It is up to the council cabinet to make the final decision anyway, although it is important for the council to have the opportunity to express their opinion. We have not been keeping members in the dark."

He said the proposed sites were only known to members of the Waste Treatment Board, made up of representatives from the county and district councils.

A contract is expected to be signed in 2009, with the incinerator operating by 2012 or 2013.