A third runway at Heathrow airport is expected to get the go-ahead today, despite opposition from environmental groups, Labour backbenchers, local councils and residents.

The announcement by Geoff Hoon, the transport secretary, is certain to trigger a legal challenge.

However, the Government could make concessions such as a new high-speed rail link between the airport and central London.

Airlines could also be required to use only the latest planes in new runway slots in order to reduce noise and pollution.

The 2,200 metre-long third runway, which will run parallel to and north of the existing runways, would be completed by about 2019/20. The £9 billion airport expansion will also include a sixth terminal.

Mr Hoon is likely to argue that the whole of the UK will suffer unless there is expansion of the country's biggest airport.

BAA, which owns Heathrow, claims the existing two runways are operating at 99 per cent of their capacity.

Unions in favour of the expansion say it will create 65,000 jobs.

However, building the new runway will effectively destroy the village of Sipson.

The number of flights at Heathrow will be increased from about 480,000 a year to 700,000, emitting nearly 27 million tones of CO2 every year – as much as the emissions of the 57 least polluting countries in the world combined.

Greenpeace, who has bought a piece of land earmarked for the development, said the new runway “cannot and will not be built”.

John Sauven, the director of Greenpeace, said: “If it's a green light it will shred the last vestiges of Brown's environmental credibility. An expanded Heathrow would become the single biggest emitter of CO2 in Britain.

“Labour MPs will lose seats over this as the anti-runway movement grows and grows. We'll fight it every step of the way because the lives of millions of people depend on us all slashing carbon emissions."

Boris Johnson, the Mayor of London, has pledged £15,000 of public money to challenge the expansion in court.

Liberal Democrat MP for Richmond Park Susan Kramer, who is also leading her party’s campaign against Heathrow’s expansion, said: "We will never give up this battle.

“The battles for quality of life in our area and on climate change are simply too important for us to give up. The Government brought this fight to us, but they will regret it."