Advocates of a third runway at Heathrow airport will be able to make their case in a consultation process to be launched in the next few weeks, Downing Street confirmed on Monday.
But prime minister David Cameron's official spokesman said that the Government's position was unchanged since the coalition agreement of 2010, which committed ministers to scrapping plans drawn up by the previous Labour administration for a third runway at Heathrow.
Chancellor George Osborne yesterday sparked speculation over a possible u-turn by saying he believed more runway capacity was needed in the South-East of England and all options should be examined.
Transport Secretary Justine Greening - whose Putney constituency lies under Heathrow flightpaths - has been a vociferous opponent of a third runway and it is thought that her fate in the Cabinet reshuffle this week may rest on the Prime Minister's plans for aviation policy.
Mr Cameron's spokesman declined to confirm press reports suggesting that a commission of outside experts is to be created to conduct an independent review of Britain's airports, effectively taking the decision out of politicians' hands.
But he confirmed that a consultation process would be announced within the next few weeks, with all sides being given the opportunity to put their views - including proponents of a third runway.
The spokesman told reporters at a regular Westminster briefing: "We said before the summer that we would come back to this issue in the autumn. We will do that in due course... We will say more about the process in the next few weeks."
He added: "The Government's position on the third runway is as set out in the coalition agreement.
"What the Chancellor said was that he believed that there was a case for additional capacity in the South-East and we should look at all the options.
"There are strong views about this issue on both sides of the argument. Any process must involve listening to those views and, therefore, I would expect all the options to be considered within that process.
"If we are going to listen to people's views, there are people who are making the case for the third runway who I am sure will make that case.
"There's a coalition programme for government that sets out the position on that, but I think there is going to be a debate about this issue and I would expect the people in favour of that proposal to put forward that proposal. The coalition programme commitment remains."
MP and environmental campaigner Zac Goldsmith said he would not be a Tory candidate at the next general election if the party did not explicitly oppose a third runway for Heathrow.
"I think the arguments that are put forward in favour of Heathrow expansion are based on wild exaggerations," he told BBC Radio 4's World at One.
"Heathrow is already one of the busiest airports in the world."
The MP for Richmond Park and North Kingston went on: "I think if we enter the next election with a manifesto which does not rule out expansion of Heathrow I think the Conservative Party will be very badly defeated in areas beneath the flightpath.
"I personally would not want to stand as a Conservative candidate on a manifesto that is ambiguous on this issue. I think we need to be very, very clear and honest with voters."
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