Labour leaders could vote against allowing a third runway to be built at Heathrow due to environmental concerns about pollution.
The government wants to go ahead with Heathrow expansion but a final vote will not be taken in the House of Commons until 2018.
Labour has acknowledged the need for extra runway capacity in the south-east but has raised questions about the potential pollution and reduction in air quality created by Heathrow expansion.
Party sources have told the Financial Times that Labour leader Jeremy Corbyn is likely to vote against Heathrow expansion. Shadow chancellor John McDonnell is also an opponent of a third runway.
One Labour source told the FT: "It has to pass our tests and no one here expects that to be likely”; while another said: “If the vote is any time soon there is no way we would back it, mainly on the basis of air quality, and that’s unlikely to change any time soon.”
Several members of the Conservative cabinet, including foreign secretary Boris Johnson and education secretary Justine Greening, are also fiercely opposed to Heathrow expansion and will be allowed to continue opposing it despite the government’s official policy.
This could mean that Theresa May’s minority government will have to rely on support from other parties, such as the SNP, to get the Heathrow vote through parliament.
Labour’s apparent change in stance towards Heathrow expansion was criticised by some within the business travel industry.
Jason Geall, general manager for Northern Europe at American Express Global Business Travel, said: “It is disappointing to learn the Labour party has indicated that it is likely to vote against the expansion of Heathrow airport when the issue comes before parliament.
“Labour previously expressed its concerns regarding the proposed third runway at Heathrow, but appears somewhat short-sighted to oppose the plans at this stage given that during the general election campaign a few short months ago the leadership had already committed to expanding airport capacity in the south east.”
The GTMC said the reports about Labour's potential opposition to Heathrow expansion were "frustrating".
“Reports today that plans for a third runway at Heathrow could be opposed by the Labour party leadership and some Conservative MPs are frustrating, detrimental to the economy and severely short sighted," said a GTMC spokesperson.
"As the voice of the business traveller, the GTMC is very clear that airport expansion in the south east is vital for the UK’s continued economic growth, particularly post-Brexit."