Justine Greening has said the government remains opposed to a third runway at Heathrow, despite calls from Conservative MPs for a change of heart.
The transport secretary said expanding Heathrow was "not right" for the UK and other options needed to be considered - including building a new hub airport.
Some ministers have reportedly urged a rethink amid strong business support.
And backbencher Tim Yeo said David Cameron must show whether he was a "man or a mouse" by backing the idea.
The coalition agreement between the Conservatives and the Liberal Democrats rules out any expansion of Heathrow before the next election, while Labour also currently opposes the idea of a third runway at the UK's largest airport.
But a consultation on future air capacity in south-east England has twice been delayed amid reported divisions within the coalition and Conservative ranks.
Ms Greening, whose Putney constituency is on the Heathrow flight path and who personally campaigned against a third runway before becoming a minister, said the coalition agreement was "very clear" in its opposition to a new runway at Heathrow.
"I don't think any of the facts have changed around a third runway," she told Radio 4's Today programme. "The facts remain as they were at the time of the election."
She said concerns over increased noise, pollution and disruption to the surrounding area had not been addressed and suggested that a new runway would not be long enough to accommodate new, larger planes and would be full "within a few years".
"There is now a cross-party consensus that a third runway... is not the right thing for Britain," she said.
"Make no mistake - a third, short runway will not be a long-term solution to our country's hub capacity question that we currently face.
"Britain deserves better and deserves a much longer-term aviation plan than it has had in the past."
The idea of a new airport - like one proposed by London Mayor Boris Johnson in the Thames Estuary - was "clearly one of the options", she added, as well as existing airports working more closely together.
Asked about her own position, Ms Greening said she would find it "difficult" to remain in government if it reversed its position on the issue, while insisting this was a "hypothetical" situation.
Chancellor George Osborne said it was not a decision that could be made "right here, right now".
"We are absolutely clear we do need additional airport capacity, particularly in the south east of England, which is the most congested part of the country when it comes to air traffic. Exactly where that capacity is, is something we've got to listen to people on," he told the BBC.
Since then, a number of Tory MPs have warned that the UK is being left behind in aviation, saying a new runway is needed to boost trade and competitiveness.
Housing Minister Grant Shapps, tipped for promotion in a reshuffle, said on Friday that "all the options need to be considered while being mindful of our election manifesto".
And Mr Yeo, chairman of the Commons energy and climate change committee, said his long-held "environmental objections" to Heathrow expansion were "disappearing".
He told the Daily Telegraph that European Union carbon emissions caps would force airlines to use more environmentally friendly planes if they wanted to use new capacity at Heathrow.
And he added: "The prime minister must ask himself whether he is man or mouse.
"Does he want to be another Harold Macmillan, presiding over a dignified slide towards insignificance?
"Or is there somewhere inside his heart - an organ that still remains impenetrable to most Britons - a trace of Thatcher, determined to reverse the direction of our ship? Let's go for it."
He later told BBC Radio 4's The World at One that circumstances had changed since the coalition agreement and the prime minister faced a "moment of opportunity" to alter the government's position.
"It's a mark of mature and effective leadership for a government to be able to say 'look we made a commitment then. We now realise the situation has evolved in a pretty unhelpful way economically so we're going to take a different decision'," he said.
The coalition government scrapped Labour's plans for a third runway when it came to power, following widespread opposition from councils, residents and green groups.
Both Downing Street and Deputy Prime Minister Nick Clegg insisted on Tuesday that the government would stick to its pledge not to build a third runway.
The BBC's political editor Nick Robinson said the business community saw the future of Heathrow as a "totemic" issue regarding the government's ability to take long-term economic decisions.
But he said the prime minister would think long and hard before countenancing any change, mindful of his party's election promise and the damage that the U-turn over tuition fees did to the Lib Dems.
As the debate over Heathrow's future intensifies, Boris Johnson said it would be "totally wrong" for a new runway to be built there.
"I don't think Heathrow represents the answer and I think the prime minister understands that," he said, adding that the consultation must begin as soon as possible.
Labour also urged the government to move forward with the consultation.
"Political parties should work together to develop a sensible and sustainable alternative to the rejected Heathrow third runway and the unworkable fantasy Thames Estuary proposals," the party said.
Friends of the Earth said it welcomed the government's continued opposition to a third runway, but added there was no need for further airport expansion in the south east of any kind.
"Ministers should prioritise better public transport and encourage people to use trains instead of environment-wrecking short-haul flights," the group said.