A pre-action protocol letter has today been sent to Environment Secretary Caroline Spelman, informing her of the council's intention to challenge her decision to award �91m in Waste Infrastructure Credits to Norfolk County Council to build an incinerator in King's Lynn.

Late last year, Ms Spelman warned the county council she was concerned at the strength of opposition to the project.

She requested evidence that there was 'a broad consensus of support' in favour of the incinerator.

But last month, Ms Spelman announced that she had decided to award the �91m in waste credits neeeded to build the plant at saddlebow, near Lynn.

This week it emerged the county council had signed the contract with US consortium Cory Wheelabrator to build and run the plant.

West Norfolk council is seeking a judicial review of the decision to award the waste credits. More than 65,000 West Norfolk people said they did not want the plant, in a council poll.

Tonight West Norfolk council leader Nick Daubney said: 'It is regretful that it has come to this, but we have been frustrated at every turn by Defra's apparent unwillingness to engage with us throughout this process.

'We have telephoned, e-mailed and written to the Secretary of State's office asking for copies of the evidence and so far this has not been forthcoming.

'None of this is surprising given that prior to the Secretary of State's decision being announced, we had written to her on no less than 12 separate occasions without receiving a response and all my requests for a meeting were not even acknowledged.

'It is shocking that a decision of such magnitude can be taken with such a lack of transparency.

'The Pre-Action Protocol letter that we have sent today places a duty upon the Secretary of State to disclose the evidence and information that convinced her to change her mind.'

Bill Borrett, Norfolk County Council's cabinet member for environment and waste, said: 'It's between the borough council, Caroline Spelman and Defra.

'It's Caroline Spelman's decision they have a problem with, it's really nothing to do with Norfolk County Council.'

The pre-action protocol letter requires Ms Spelman to provide copies of all evidence received between November 7 and January 18, which led her to conclude that her criterion for the award of the credits had now been satisfied, when previously, she had said that she was not satisfied it had been met. The secretary of state has until February 27 to provide the evidence supporting her decision.