Campaigners have pledged they will not give up the fight to stop an incinerator from being built in Norfolk, despite the government releasing millions of pounds for the plant.

And the leader of West Norfolk Council has warned environment secretary Caroline Spelman he is ready to launch a High Court challenge unless she can justify her decision to bankroll the King's Lynn incinerator.

Mrs Spelman had with-held government funds from Norfolk County Council for the Saddlebow scheme because she wanted to be convinced there was a 'broad consensus' for the waste strategy.

Critics insist that consensus has not been proved, with West Norfolk Council and Norwich City Council both against incineration, but she announced yesterday that County Hall would get its grant from the Department for Environment, Food and Rural Affairs.

In a letter to county council leader Derrick Murphy, she confirmed a �91m Waste Infrastructure (WI) grant, which County Hall say will be worth up to �169m over 25 years, would be issued.

That money will be used by the county council to pay Cory Wheelabrator to deal with 170,000 tonnes of waste generated by Norfolk households a year.

Mrs Spelman said in her letter that she had 'been considering particularly carefully the unusually high level of local public concern' and West Norfolk Council's withdrawal from the waste partnership.

But she said: 'Local opposition is not, in itself, unusual in major energy from waste projects and is something which the planning system is well placed to weigh in reaching its judgement on whether the project should proceed.

'The relevant criterion for my department's waste infrastructure credits does not therefore require support for the project itself at local level but rather that there is a broad consensus on a recognised long-term waste management strategy and that the project is consistent with that strategy.

'We consider that 'broad consensus' does allow for some dissent and does not in particular require unanimity amongst the interested local authorities.

'Having carefully considered your project's case for waste infrastructure credits in the light of all the information available to me, including the additional material you provided in response to my recent letter and evidence of support for the strategy from most of the participating councils but opposition from King's Lynn and West Norfolk Borough Council, I have concluded that your project does meet my criteria for support.'

She said she hoped the county council would share her 'continuing concern that the project is generating such strong negative feelings locally' and urged all local authorities and the contractor to put 'fresh effort into working constructively.'

Bill Borrett, cabinet member for environment and waste, said: 'We are pleased the government has decided to support this project, which is of significant strategic importance for the people of Norfolk, and that the Secretary of State is satisfied that it meets her criteria for a grant.

'The grant represents the largest amount of central government funding for a single project that this council will have ever received.

'It will substantially reduce the cost of a proposed new service for dealing with Norfolk residents' waste, making it excellent value for money – and very good news for the county's council taxpayers.'

A number of district council leaders had penned letters to Mrs Spelman supporting the waste strategy, although West Norfolk Council leader Nick Daubney and some opposition leaders on district councils pleaded with her not to be swayed.

Critics pointed out those leaders had not consulted their own councils before sending the letters and campaigners had hoped an 11th hour letter from Norwich City Council's leader Brenda Arthur, re-iterating that the authority was against incineration would see Mrs Spelman pull the plug on the credits.

However, despite yesterday's decision to grant the credits, campaigners said the fight would go on, with the plant still needing to secure planning permission and an environmental permit.

Nick Daubney, leader of West Norfolk Council, which conducted a poll where some 65,000 people said they were against incineration, said his authority has set aside �250,000 for a legal challenge.

He said: 'I am perplexed because she asked Norfolk County Council for more evidence of a consensus of support, but since then it has deteriorated because now Norwich City Council has said it is against it.

'I have emailed her asking to see the evidence and I hope she instructs her civil servants to provide that. I need her to share it so I can understand how she has arrived at this decision.

'If that is, in our view, unsatisfactory, then we will look to go to a judicial review.'

Campaigner Michael de Whalley, who led the ultimately unsuccessful attempt to get a judicial review into the county council's decision to agree to award a contract for the incinerator, said the battle was not over.

He said: 'Caroline Spelman's decision is flawed and we expect that the borough council will seek a judicial review over it and we will support that as much as we can.

'It is very frustrating that a government elected on a mandate of empowering local communities has come out with a statement to the effect that local opposition does not count.'

With the plant needing to secure planning permission, it is understood a further round of consultation will begin on Monday.

Mr de Whalley urged opponents to the scheme to make their voices heard through the planning process. A recent council report revealed there had been 2,550 objections to the proposal - more than 96pc of all comments received.

dan.grimmer@archant.co.uk