An immediate legal challenge could be issued if the government agrees to give Norfolk �169m in PFI (Private Finance Initiative) credits to build an incinerator, it emerged today. It came as Environment Secretary Caroline Spelman's office confirmed she has still not decided whether to rubber stamp the deal.

Ms Spelman delayed the award of the credits last year as opposition mounted to plans to build the so-called energy from waste plant at Saddlebow.

She wrote to county council leader Derrick Murphy, saying the county needed to show proof that there was a broad consensus of support behind the plan.

Today West Norfolk council leader Nick daubney said: 'We're taking advice on this because of what she put in that letter to Derrick Murphy, we have every right to take legal action.'

West Norfolk council set aside �250,000 to fund legal action against the incinerator, after more than 65,000 West Norfollk residents voted against it in a council poll.

When the county council published Cory Wheelabrator's planning application to build the incinerator, it received 2,639 responses, 2,550 of which were opposed.

Many expected an announcement to be made this week, with some predicting that the PFI deal would be approved.

But today an official at Ms Spelman's office said: 'We will be making a decision in due course - it's still under consideration.'

Earlier, an MP warned the minister would be 'in blatant contradiction of her own guidelines' if she agreed the deal.

North West Norfolk MP Henry Bellingham told campaigners that a decision to award the money could be overturned by the courts.

'If Caroline Spelman does give the green light to PFI credits, then this obviously would be in blatant contradiction of her own guidelines,' Mr Bellingham wrote.

'I would be quite staggered if it was not judicially reviewed, and I would also anticipate that there would be a very good chance of the case being won.

'For my part, I am doing all I possibly can to make her see sense; furthermore, I plan to go on fighting this every inch of the way during the planning process.'

Mr Bellingham could not be contacted this afternoon. Campaigner John Martin, who received the e-mail, said: 'Caroline Spelman may be under intense pressure from the waste industry to make a sacrificial lamb out of Norfolk.

'However, she will be skating on thin ice, should she choose to do so. It is becoming increasingly clear that 2006 Joint Municipal Waste Management Strategy for Norfolk was never intended to support the principle of a mass burn energy-from-waste incinerator in King's Lynn - or anywhere else in the county.

'This is despite what a number of our district council leaders would have her believe'

Earlier this week Norwich City Council wrote to Ms Spelman underlining its opposition to incineration.

Mr Daubney said: 'We now have the two largest councils, representing a third of the population, saying we don't support it.'

The incinerator has already seen one failed legal challenge. Campaigners failed to win leave for a judicial review of the county council's conduct in awarding the contract to build and run the plant.