Downing Street has insisted the Government will not back down on its opposition to a third runway for Heathrow, amid growing unrest among Tory MPs over Britain's future airport capacity.
No 10 brushed off an outspoken attack by senior Conservative backbencher Tim Yeo who challenged David Cameron to show if he was "man or mouse" and defy his critics by reversing policy on the issue.
His intervention prompted fresh demands from fellow Tories for ministers to finally grasp the issue and address the country's long-term aviation needs.
Ministers could be in for a rough ride when MPs return to Westminster next week following the summer break, with concern over the issue tapping into a wider sense of unease about the struggling economy.
Downing Street insisted the Government is sticking by its commitment in the coalition agreement that there would not be a third runway at Heathrow.
"The coalition parties have made a pledge not to have a third runway and that is a pledge that we will keep. We don't see the argument for a third runway," a No 10 spokeswoman said.
Transport Secretary Justine Greening, whose Putney constituency lies under the Heathrow flight path and who has campaigned against a third runway, warned she would find it "difficult" to remain in the Cabinet if the policy changes.
Nevertheless she will be under pressure to press ahead with the promised consultation on future airport capacity, with Chancellor George Osborne reported to be among those warning that the future needs of business must be addressed.
Mr Yeo, a former environment minister and chairman of the Commons Energy and Climate Change Committee, denied that he is "throwing down a gauntlet" to the Prime Minister.
Writing in The Daily Telegraph, he said that an immediate decision to give the go-ahead to a third runway would show that his Government has found its "sense of mission".