A £565m black hole exists in the Government's figures for the cost of building new runways and infrastructure at Stansted Airport, a report will claim on Thursday.
Produced by consultants Berkeley Hanover, the report will challenge the Government's claim that improving the road and rail infrastructure around the airport will cost up to £1.88bn.
Berkeley, which has previously worked for Deputy Prime Minister John Prescott, is expected to claim that the real figure could be as high as £2.45bn.
The report has the backing of shadow financial secretary Mark Prisk. It was commissioned by Uttlesford District Council and the Stop Stansted Expansion Campaign, which counts TV chef Jamie Oliver as a member. Transport Secretary Alistair Darling must decide this year between: building a third runway at Heathrow; two at Gatwick; a new airport at Cliffe in Kent; or up to three new runways at Stansted.
It is understood that Berkeley Hanover will challenge the figures in the Government's South East Regional Aviation Study (Seras). This predicted that three new runways at Stansted would generate up to 270,000 average daily car trips by 2030 and 43,000 rail journeys .