Controversial plans for a third runway at Heathrow Airport are expected to be signed off by senior ministers, triggering a battle to push the scheme through Parliament.
The divisive issue is said to be on the agenda for Prime Minister Theresa May’s meeting with ministers on the Cabinet’s economic sub-committee on Tuesday morning.
The committee is expected to sign off the Airports National Policy Statement (NPS) before putting it before the full Cabinet for approval, BBC News reports.
Transport Secretary Chris Grayling is likely to then make a statement to MPs, who are expected to be given a vote on the NPS in the coming weeks.
Proponents of building a third runway at the major hub said it is the best option to increase capacity and boost the national economy while being cost-effective.
But critics warn the plan is "expensive and complex" and bad for the environment.
One group hinted legal action may be taken against the Department for Transport (DfT) over its "dodgy" handling of the process.
Alternative schemes include expanding Gatwick Airport in Surrey.
Any announcement in favour of a third runway is likely to be met with dismay by MPs from across the divide whose constituencies are already affected by Heathrow air traffic.
According to reports, Foreign Secretary Boris Johnson, the MP for Henley, could be forced to vote against the Prime Minister, while former transport secretary Justine Greening, who represents Putney, has also been a vocal critic.
On Monday, Liberal Democrat leader Sir Vince Cable, whose Twickenham seat stands to be affected by expansion, branded the scheme "ill-conceived".
Heathrow Airport through the years - In pictures
Extend the Runway, a group advocating increasing capacity by lengthening the airport's northern runway, said the DfT "lacks both expertise and attention to detail" and had not listened to its proposal.
"People should have zero confidence that the DfT ave run a rigorous process on Heathrow's expensive and complex plan," the group said on Twitter.
The No Third Runway Coalition, which counts Sir Vince and Labour shadow chancellor John McDonnell among its members, said the DfT's process had been "dodgy and has favoured Heathrow Airport Ltd from the start".
"That will be proven in court, if it comes to it," they added.
The Aviation Environment Federation said it is "extremely unlikely that the Government will have been able to find solutions to key challenges related to the environmental impacts of expansion".
The group said: "The Aviation Strategy, which is being taken forward under a separate process to the Heathrow NPS, will set out how the environmental impacts of aviation nationally should be tackled, but will not be consulted upon until later this year with publication of the final strategy not expected until the middle of next year.
"The decision on Heathrow is set to be taken, therefore, in the absence of any policy on how to tackle aviation's carbon emissions, so with no clarity on whether limits on aviation growth will be needed in order to meet climate change obligations."
