BAA has said it hopes to launch a public consultation on a third runway at Heathrow within a year.

The air operator has continued to work on a planning application in the lead up to a general election - despite the Conservatives, who are ahead in the polls, promising to scrap the contraversial project.

But BAA confirmed it will not take the next step towards expansion until after May 6, the expected date of the election.

Campaigners were confident that - one year after the Government approved a third runway - their chances of victory were growing.

John Stewart, chairman of campaign group Hacan, said: “A year ago it looked like a third runway would be built at Heathrow, but a year on that now seems like a distant prospect.

“It’s now clear that unless Labour wins the next election a third runway at Heathrow will not happen. I think we feel that the big decision will come just after the election.”

The 2M Group, a coalition of councils opposed to expansion, will join campaigners in a High Court legal battle next month to challenge the process that led up the the Government’s go-ahead.

Mr Stewart said the timing of the case was “perfect” as it will focus politicians’ minds on the debate ahead of the election.

BAA said it expected “to be in a position to consult with local residents and all other interested parties in the second half of 2010.”

A spokeswoman for BAA said: “The timing of any planning application and its component parts are not influenced by anything other than the requirements of the infrastructure planning commission (IPC) and the large volume of work needed to put together a robust and compelling application."

But Mr Stewart said: “We are now in a situation where we will be surprised if it will go ahead.

“I think BAA are doing a little bit of work, but I think they are not putting much money into preparing for a third runway until the election, any business wouldn’t be because of the uncertainty.

“While they are publicly saying they will, I think they know as well there’s real question marks as to whether it will go ahead.”