Foreign Secretary Boris Johnson has branded Heathrow expansion a "fantasy" destined for the "dustbin".
His fiery remarks came after the ex-mayor of London was excluded from the key Cabinet committee that will decide on airport expansion.
The move was seen as a potential signal that Prime Minister Theresa May is getting ready to approve a new runway at Heathrow.
Mr Johnson warned that the taxpayer would foot the bill for the inevitable failure of Heathrow expansion.
"As I've advocated for many years Heathrow expansion is the wrong choice, and if it is chosen it simply won't get built," he said.
"The massive costs and enormous risks mean it's undeliverable, and the taxpayer will be saddled with the bill for failure.
"While we are finding this out our international competitors will be further extending their competitive advantage over us. We need to consign this Heathrow fantasy to the dustbin. We need a better solution," Mr Johnson said, the Daily Telegraph reported.
It is understood that Mr Johnson will still contribute to the debate due to his eight years' experience as London mayor and as the MP for Uxbridge and South Ruislip, near Heathrow.
The long-awaited decision on whether to expand Heathrow or Gatwick is politically highly sensitive for the Prime Minister due to divisions within the Tory ranks.
Mr Johnson campaigned against Heathrow expansion while he was mayor, and Putney MP and Education Secretary Justine Greening is also opposed.
Although, as Foreign Secretary, Mr Johnson does not hold a direct interest in airport expansion as part of his job, the decision will affect his brief in terms of Britain's links with the rest of the world, as a new runway could open up new destinations for direct flights.
A Downing Street spokeswoman said: "We will confirm membership of the Cabinet committee in due course."
The previous Cabinet committee on airport expansion, set up by David Cameron, included the then-chancellor, business secretary, transport secretary, environment secretary, Scottish secretary, communities secretary, energy secretary, chief whip and fixer Oliver Letwin.
It emerged last week that ministers may be given a free vote on the issue.
An internal Government paper filmed by a passenger on the London Underground discusses the "potential waiving of collective responsibility" ahead of the forthcoming decision on airport capacity.
In July last year the Davies Commission recommended the building of a third runway at Heathrow, but the Department for Transport announced that further investigation into noise, pollution and compensation would be carried out before a decision is made.
Mr Cameron was expected to indicate which project would get the go-ahead after the EU referendum, but his resignation following the victory for the Brexit campaign meant the decision was left for his successor, Mrs May.
A group of political and business leaders have written to the Prime Minister urging her not to give the go-ahead for a third runway at Heathrow.
Expansion at the London hub would "re-forge its monopoly" in the UK, the 29 signatories said in their letter to Mrs May.
The group, which includes the chief executive at Birmingham Airport, Paul Kehoe, and a number of West Midlands MPs, pleaded with Mrs May to ensure the decision on extra runway capacity does not damage the region.