The planning inspector who agreed plans for Terminal 5 has spoken out against the Government's plans for a third runway and sixth terminal at Heathrow Airport.

In a TV interview public inquiry inspector Roy Vandermeer said: "At the moment I have not for my part seen enough to persuade me that I would be altering my recommendations about the third runway, were I doing it now.

"But that's not to guarantee I wouldn't, but I have not seen the material that would make me convinced that I would change my mind."

Clive Soley, campaign director of Future Heathrow, a coalition of businesses and groups from the aviation industry said: "It seems as if Mr Vandermeer is being cautious in what he says.

"What he needs to look at is the expansion of airports in Frankfurt and Paris and then ask, how can Heathrow stay as a hub airport if we do not expand?

"The number of destinations served by Heathrow has gone down while at other competing hubs they have gone up, therefore the future of Heathrow is grim unless we expand."

Mr Vandermeer recommended that T5 be built after a public inquiry that lasted nearly four years, the longest in UK history.

He said the project should go ahead on the condition that the number of flights be capped at 480,000 per year.

The Government accepted the limit when it gave T5, which is due to open to the public in March, the official green light in 2001.

If a third runway goes ahead and runway alternation ends in favour of a mixed-mode landing schedule there could be about 800,000 flights at Heathrow.

John Stewart, chair of the campaign group HACAN, said: "Just how many knowledgeable people need to speak out against expansion before the Government will listen?

"It is time Gordon Brown listened to independent experts rather than forever being swayed by the self-interested, siren voices of the aviation industry."