The Government's environmental case for expanding Heathrow is based on plans for futuristic planes which may never be realised, it was claimed last night.
Ministers claim low-emission planes being developed mean thousands more flights will be possible by 2030 with no increase in pollution.
But an episode of Panaroma aired yesterday evening claimed such planes are not even in the development pipeline.
The show explored allegations ministers are 'in cahoots' over Heathrow with industry leaders, many of whom previously worked for the Government.
The airport's owner BAA wants to build a third runway and sixth terminal which would allow an extra 220,000 flights a year by 2030.
Denying allegations of a collusion with BAA on last night's show, aviation minister Jim Fitzpatrick said: "This is pure transparecy - everybody knew we would be talking to them.
"What we have done is check their figures - we've double checked them and the documentation which has been produced is not BAA figures - these are our figures and our documentation."
But John Stewart, chairman of anti-expansion campaign group HACAN, said: "With every new revelation the Government’s plans to expand Heathrow are becoming more and more discredited."
The Department for Transport has not yet commented on the claims.