Ministers have postponed a decision on whether to allow Heathrow to build a third runway, in move that has been taken as indicating a possible weakening in support for the project.

A decision had been expected this month on whether Heathrow, the world’s busiest international airport, would be allowed to add an additional runway.

However Geoff Hoon, the Transport Secretary, said today that a decision would now be made by the end of January 2009.

The third runway proposal is controversial because of the increased noise and environmental pollution it would create.

More than 50 Labour members of parliament have backed a motion calling for the third runway to be scrapped and the Conservatives are also against the proposal.

BAA, the airports operator, and British Airways, the largest airline operating from Heathrow, have said that the UK’s principal airport needs extra capacity in order to remain globally competitive.

In a statement, BAA said: “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.”

The decision on a third runway at Heathrow has been repeatedly delayed by the government as opposition has mounted and alternative proposals have been offered.

Boris Johnson, the Mayor of London, has suggested building an entirely new airport in the Thames Estuary, east of London.

Theresa Villiers, the Shadow Transport Minister, said: “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.

"We need to make Heathrow better, not bigger, and the best way to do that is to provide a high-speed rail alternative to thousands of short-haul flights now contributing to the overcrowding problems at the airport.”

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