British PM David Cameron
The controversy over Heathrow's future after Tuesday's cabinet reshuffle has increased after Boris Johnson urged expansion to be permanently ruled out.
The removal of Transport Secretary Justine Greening, a fierce opponent of Heathrow expansion, has led critics to say ministers may change their mind.
Conservative MP Zac Goldsmith said it was unfair to leave people "in limbo".
But new party chairman Grant Shapps said there was "no chance" of a change in policy before 2015.
Shapps told the BBC that the Conservatives would not go back on their pledge not to expand Heathrow during this Parliament and this was "absolutely guaranteed".
But he said options had to be kept open for the future.
The row came ahead of the first meeting of David Cameron's new cabinet and the first Prime Minister's Questions since MPs returned to Westminster.
David Cameron is continuing to finalise the appointment of junior government ministers, the culmination of the most extensive reshuffle since the coalition came to power in 2010.
Among the most notable changes, Jeremy Hunt became health secretary, Chris Grayling was promoted to justice secretary and chief whip Patrick McLoughlin took over as transport secretary from Miss Greening - who was given a less high profile role at international development.
The decision to move Miss Greening - who had only been in the job ten months - has sparked a row with Boris Johnson saying the only reason to make the change was to signal a change in policy on Heathrow and aviation capacity in general.
The government has ruled out approving a new runway before 2015 but Johnson said there were increasing signs that a "u-turn is in progress".
"What we need to do now is to end the uncertainty over Heathrow and say 'no folks it is all right, the policy is as it has been which is to say no to a new runway both now and in the future - i.e. in the next two and a half years."
The BBC News Channel's chief political correspondent Norman Smith said Johnson wanted to kill the idea of a third runway for ever and this was a "marked escalation" of the dispute within the party over the issue.
And MP for Richmond Park Zac Goldsmith, who has threatened to resign and trigger a by-election if the government does a U-turn, said ministers had "to get off the fence" over the issue.
"It is not fair to voters in constituencies like mine to keep them in a state of limbo. They need to know whether they (ministers) have changed their mind."
Grant Shapps, the new Conservative Party chairman, said there was a shortage of airport capacity in the south of England and it would be "irresponsible" for ministers to rule out any long-term options to ensure the UK remained a "great trading nation".
But he added: "There will not be a third runway at Heathrow. We have made that commitment for this Parliament and there is no chance of it being broken whatsoever."
"The third runway will not be built in this Parliament, that is absolutely guaranteed."
The reshuffle came amid criticism from many Conservative MPs that the coalition was not doing enough to restore economic growth in the face of the ongoing recession.
Some expressed delight that Cameron had promoted some on the right of the party, including Grayling and McLoughlin.
But Deputy Prime Minister Nick Clegg insisted the coalition "remains anchored in the centre ground".