The government's rejection of a £1bn waste incinerator near St Albans has been ruled illegal by the High Court.

The heat-from-waste burner on green belt land at New Barnfield will now be reconsidered by Secretary of State Eric Pickles.

Waste firm Veolia won its appeal by claiming government rules on planning and waste had been ignored.

Mr Justice Holgate at the High Court last Thursday said Mr Pickles got it wrong in balancing harm to the green belt with the need for the incinerator.

Planning inspectors had turned down the huge processing plant, saying it was an "inappropriate" development.

Conservative MP Anne Main has slammed the decision-making process. She said: "It’s outrageous that local planning decision-making is being overturned by the courts in favour of the developers.

"It is not without irony that Veolia was citing the decision by the Secretary of State to be ‘minded to grant’ on the Park Street rail freight as an example of why they should have special consideration; and that St Albans was citing Veolia as a reason to justify our refusal of the rail freight.

"My constituents can be forgiven for thinking that there appears to be a lack of coherent legal advice given to the Secretary of State which is giving rise to these inconsistencies.

"I know residents on the eastern side of my constituency were deeply unhappy at the initial proposals and welcomed a refusal; this decision will now place uncertainty on the matter.

"Therefore, I can only hope we have a speedy resolution and the original refusal is upheld - I’ll be monitoring developments very closely."

Hertfordshire County Council has spent nearly £6m supporting the project. Terry Douris, cabinet member for highways and waste management, said: "We acknowledge the judgement regarding Veolia’s High Court challenge.

"The county council will continue to follow developments regarding this case while awaiting a revised project plan from Veolia. We are fully aware that there have been concerns in the local area about these plans and we remain sensitive to these."

The proposal was for the demolition of existing buildings and the construction and operation of a RERF to treat municipal, commercial and industrial wastes, together with ancillary infrastructure landscaping, habitat creation, drainage and highway improvements.

The RERF would be able to treat up to 380,000 tonnes of municipal and industrial waste per year.

Green party councillor Simon Grover said the news was a shock. He said: "We all thought this battle was over.

"We can only hope that the Secretary of State will now end the matter with a clear and unambiguous decision.

"It would be madness for the County Council to go ahead with the incinerator when there are cleaner, greener and cheaper alternatives available. This whole saga has shown the folly of Private Finance Initiatives, in which successive governments have offered eye-watering sums to private companies to run public services such as waste management, hospitals and prisons. The policy is and always has been a disgraceful waste of taxpayers' money."