The anti-airport expansion group Climate Rush held a protest in Terminal One
Opponents of the construction of a third runway at Heathrow have staged a protest at the airport ahead of a government announcement on the project.
Crowds of campaigners, some in Edwardian costume, sat down to enjoy a picnic in the airport's Terminal One.
It comes as Gordon Brown, who is expected to agree the plans, says he will meet Labour MPs against expansion.
Unions and business leaders have joined the airline industry in urging the government to approve the construction.
The Future Heathrow Group warned in newspaper adverts "Heathrow's status as a global hub is at stake". The union Unite says 172,000 jobs may be at risk.
'Gateway to world'
The Future Heathrow Group's adverts say the expansion is vital for the British economy's long-term competiveness.
Heathrow's modernisation is the only way to reduce aircraft emissions and cut disruption
Derek Simpson, Unite
It argues other major European airports have already expanded and are ready to take advantage when the market starts to recover.
CBI director-general Richard Lambert said: "Heathrow is our gateway to the world and we need to ensure that it remains a world-class airport capable of serving the needs of a global economy."
Baroness Jo Valentine, chief executive of business group London First, said: "Business needs to fly and will do so long after the current economic turmoil."
The union Unite said Heathrow's modernisation would not only safeguard jobs but create an additional 50,000 in construction and services.
Joint general secretary Derek Simpson said: "We sincerely believe that Heathrow's modernisation is the only way to reduce aircraft emissions and cut disruption."
If the government pushes ahead with their disastrous plans they are going to be met with peaceful but determined public protests
Airport operator BAA says it needs to build a new runway to meet passenger demand.
But the Institute of Public Policy Research think-tank said conditions for meeting noise and emissions targets must be attached to any approval of the third runway.
Opponents, including residents living near the airport and environmentalists, are continuing to fight the expansion plans.
Police said 250 people took part in the Heathrow protest.
"This is our last chance to tell our government that they are making a big mistake," said a spokesman for Climate Rush, some of whose members dressed as suffragettes for protests at Heathrow and Manchester airports.
"If the government pushes ahead with their disastrous plans they are going to be met with peaceful but determined public protests on an unprecedented level."
About 50 people took part in the protest at Manchester Airport's Terminal 3.
Vanessa Hall, spokeswoman for the group Northern Climate Rush, said domestic flights between the city and London were "most unnecessary".
Fight to go on
At Heathrow, campaigner Dan Glass said of the protest's Edwardian theme: "It's all in the culture of the Suffragettes.
"We are trying to emulate what our ancestors did for us to make a positive change, in a civilised fashion, for future generations."
Marina Pepper, from Climate Rush, said: "We have the economy going off the cliff and we also have the genuine threat that climate change presents.
"This is no time for business as usual. If ever there was a time to take action, that time is now."
Some protesters have vowed to continue their fight even if it does get the go-ahead.
The Heathrow Association for the Control of Aircraft Noise (HACAN) and No Third Runway Action Group (NoTRAG) said they would consult their lawyers and mount a legal challenge.
BA chief executive Willie Walsh: 'We can meet the environmental restrictions'
London Mayor Boris Johnson said he expected a legal challenge and other objections would prove "insurmountable" for the project, which the Conservatives oppose.
More than 50 Labour MPs are opposed to the proposal and Environment Secretary Hilary Benn has voiced reservations about any development's environmental impact.
But at a meeting of the Parliamentary Labour Party, Gordon Brown said he would meet those sceptical about the development again.
Mr Brown told the meeting there was an intense debate on how to balance the country's economic and environmental obligations when it came to big infrastructural projects.
Friends of the Earth's transport campaigner Richard Dyer, said the government's economic case for airport expansion was "biased and fundamentally flawed".
He said it "exaggerates the benefits and underplays the costs - including the damage from climate-change".
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