A flashmob action is planned for this coming Saturday:
Ministers have approved a controversial plan to build a third runway at Heathrow, the BBC understands.
Despite opposition from residents, environmental campaigners and many of its own MPs, Labour is set to confirm the decision officially on Thursday.
Leading business and union figures back the project, saying it will create jobs and boost the UK’s competitiveness.
But critics have said it will irreparably damage the UK’s credentials on tackling climate change.
Labour unease
The government has long argued, in principle, that it is in favour of the scheme, subject to noise and air pollution limits, and undertakings about access and traffic congestion.
Alongside the commitment to a new runway, Transport Secretary Geoff Hoon is expected to announce increased investment in public transport, including a new high-speed rail link from the airport to central London.
There has been deep unease within Labour ranks about the decision, with several cabinet members reported to be unconvinced about the project and more than 50 MPs openly opposed.
In an effort to appease its critics, BBC political correspondent Jo Coburn said the government would announce new safeguards for limiting emissions with airlines using the new runway required to use the newest, least polluting aircraft.
Business Secretary Lord Mandelson defended the government’s commitment to environmental concerns over Heathrow.
He said: “It’s a classic dilemma – we want to forge ahead in implementing our climate change ambitions when others are not but we don’t want to lose our economic competitiveness in the process. We want to do both these things.”
But backbench Labour MP John McDonnell, whose constituency includes the airport, said the fight against the expansion was only just “beginning” and opponents would “use every mechanism possible” including legal challenges, to stop the runway going ahead.
“If the government is not willing to listen to Parliament or the people then there is no other option but to mobilise the largest coalition of public opposition and protest to halt this disastrous proposal in its tracks,” he said.
The Conservatives say a new runway would be an “environmental disaster” and have pledged to reverse the decision should they win the next election.
Shadow transport secretary Theresa Villiers said approval of the scheme would show Gordon Brown was “deaf to the concerns of his own party and millions of people living under the flight path”.
The Liberal Democrats have urged ministers to invest in high-speed rail links instead.
Asked about the decision on Wednesday, Prime Minister Gordon Brown declined to guarantee MPs a vote on the issue.
Should the government give the go-ahead, he said there would be a debate in Parliament and that the scheme would have to be granted planning permission.
This is likely to be a lengthy process, with work on a new runway unlike to be completed before 2019.
Public protests
Protests have been growing in anticipation of a decision, which was due to be made in December but was delayed amid reports of divisions within government over the issue.
About 700 homes will have to be demolished to make way for the runway, which will increase the number of flights using Heathrow from about 480,000 a year now to 702,000 by 2030.
Campaigners have bought some land earmarked for the construction of the runway in an effort to frustrate the expansion plans.
Environmental campaigners say proceeding with the new runway will leave the government’s legal commitment to cut carbon emissions by 80% by 2050 in tatters.
“Expanding Heathrow would shatter the government’s international reputation on climate change,” said Andy Atkins, executive director of Friends of the Earth.
“We need bold and urgent action to create a low-carbon economy, not more backing for the climate-wrecking activities of the aviation industry.”
But the government believes the new runway will not violate its EU commitments on air and noise pollution, pointing out that new aircraft being built will reduce emissions significantly.
‘At risk’
Supporters of the runway say Heathrow is already operating at full capacity and the UK economy will lose business to the rest of Europe if it does not go ahead.
They point out that rival airports such as Paris, Frankfurt and Amsterdam already have at least four runways and that Heathrow is at risk of falling further behind.
Former Labour MP Lord Soley is the campaign director of Future Heathrow, which represents groups in favour of expanding the airport.
He told BBC News that Heathrow brought jobs and “prosperity” to the surrounding areas and in an “ideal world” the expansion would not be needed.
“But the ideal world doesn’t exist and it isn’t true to say that Heathrow isn’t at risk.
“It is at risk and if it continues to decline, then the consequences for west London and the Thames Valley will be very, very serious indeed,” he said.
British Airways, the largest airline at Heathrow, has said expanding the airport is the only “credible option”.