Anti-Heathrow expansion campaigners claim the government is stalling
A decision on whether a third runway should be built at Heathrow Airport has been put back to January 2009, the Department for Transport has said.
A verdict on the controversial plans, which are opposed by environmentalists, had been expected before Christmas.
Airport owner BAA says the runway is vital for Heathrow to stay competitive.
Transport Secretary Geoff Hoon said there were "strong views" which needed "proper consideration". But the Tories accused ministers of "dithering".
It has been reported the cabinet is split over the third runway plan.
The Conservatives and Liberal Democrats oppose it and some Labour backbenchers have called for a rethink.
More than 140 MPs - including 50 Labour MPs - have signed a Commons motion urging the government to consider the alternatives to a new runway.
In a statement, Mr Hoon said the government had made it clear it supported a third runway at Heathrow - subject to environmental controls.
We had hoped for a decision before Christmas. However, having waited six years to reach this point, we can afford to wait a little bit longer
He said a consultation into the impact of such a project had finished on 9 November and he had begun to consider the evidence, including 70,000 responses.
"I share the desire on all sides of the House, and among the wider public for this issue to be resolved. I am equally aware of the importance of reaching the right conclusion," he said.
"I know that there are strong views across a range of interests. I will ensure that I give proper consideration to the evidence before me and will therefore take more time before making an announcement to the House, in January 2009."
Asked on BBC Two's Daily Politics whether he was worried that opponents of the scheme could seek a judicial review, Mr Hoon said: "I'm sure that, whatever the result, there will be those who consult their lawyers and contemplate legal action."
For the Conservatives, shadow transport secretary Theresa Villiers accused the government of "dithering on the future of Heathrow", adding: "Opposition to a third runway is gathering momentum every day.
"I suspect this postponement is an indication that Gordon Brown is finally starting to realise that he is on the wrong side of the debate on Heathrow."
Liberal Democrat transport spokesman Norman Baker said: "Let's hope this is a belated sign that the government is finally paying attention to the massed ranks of the public and the Commons benches and considering abandoning the third runway at Heathrow."
Earlier this month in a Commons debate on the issue, Mr Hoon said ministers backed the need for extra runway capacity in south east England in principle but would only approve it if air-quality and noise guarantees were met.
But he added that Heathrow was already operating at full capacity and flights and jobs would be lost to airports on the continent if nothing was done.
BAA says Heathrow, which is Europe's busiest airport, needs an extra runway by 2020 to cope with increased demand.
A spokesman said: "Given the complexity of the issues involved, we understand why the government is taking further time to consider these matters.
"We welcome the fact that the government has now committed to making a decision in January on how we keep Heathrow and this country globally competitive by maintaining our direct access to the world."
A spokesman for British Airways, which runs more flights at Heathrow than any other airline, said: "We had hoped for a decision before Christmas. However, having waited six years to reach this point, we can afford to wait a little bit longer."
'Bursting into open'
But Greenpeace executive director John Sauven Said: "The pro-runway faction in government is on the run.
"There's been whispered talk of a cabinet split for weeks, but now it's bursting into the open as more ministers realise that the business case for expansion is deeply flawed, while the environmental case for blocking a new runway is overwhelming."
Friends of the Earth aviation campaigner Richard Dyer said: "Hopefully this shows that ministers are beginning to wake up to the massive environmental consequences of allowing airports to expand."
Conservative London Mayor Boris Johnson said: "This is the second time that the government have deferred the decision on the third runway at Heathrow.
"I, like many Londoners, hope that this is an indication that they are starting to listen to reason and take seriously the concerns of the many thousands of people who would be badly affected by the scheme."
Prime Minister Gordon Brown has said a final decision will be taken after "full consideration" of the environmental implications.
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