Union leaders representing airport workers and pilots immediately welcomed the Heathrow announcement, but groups opposed to the expansion expressed dismay, vowing to continue their campaign.
Derek Simpson, joint leader of Unite, said: "This is the best decision, taken in the best interests of this country.
"The challenge now is to set to work on building an international hub airport befitting the UK's reputation as a world economy. That must include developing the high-speed rail links that will benefit every city in the land and ensure that passengers have a genuine choice of how they wish to travel.
"We fully understand that this was not an easy decision to make, but we believe that the conditions attached to the construction of the third runway will see Heathrow function as a modern, environmentally-conscious airport, and inspire a project of national works that will bring our transport infrastructure into the twenty-first century.
"There are 172,000 people and their families who depend on Heathrow for their livelihoods, plus thousands more workers in other UK airports who need Heathrow to thrive so that their airport thrives, who will breathe a sigh of relief now that this decision has been made. There are also possibly up to 50,000 more workers who will welcome the work this project will create during this time of severe economic hardship."
Mick Rix, national officer of the GMB union said, "GMB do understand the real concerns of the local people and the global environmentalists. However, the harsh reality is that we cannot stop the expansion of the international aviation industry and if we oppose it in west London it will migrate to elsewhere in Europe and with it the prosperity that it brings.
"Earnings in the London boroughs near Heathrow Airport are above the national average and GMB believes that with in a decade earnings in these areas will fall if the development of the airport is curtailed. Stopping the development would also impact adversely on the rest of the UK."
Lord Smith, chairman at the Environment Agency, said: "We remain deeply concerned about the construction of a third runway at Heathrow as air quality in the area is already at breaking point.
"This decision does put strict legal limits on air pollution. Under the new powers given to the Environment Agency as the independent regulator, we will make sure these limits are strongly and rigorously enforced."
"The CO2 and global warming impacts from increased aviation to be taken into account. Serious questions must be asked about how the aim of reaching an 80% reduction in greenhouse gases by 2050 can still be achieved in light of this decision."
Jim McAuslan, leader of the British Airline Pilots Association, said: "The UK, as with so many big infrastructure programmes, lags behind and we need a more efficient airport network across the UK including more runaway capacity at Gatwick and Stansted rather than more delaying tactics like Maplin Sands..
"Balpa especially welcomes the prospect of a new rail hub at Heathrow. But the story doesn't stop here - we need better air traffic management in the skies and on the taxiways and better ways of getting the travelling public to and from all our nation's airports.
"Our members arriving at Heathrow see the snaking queues on the M25 and the thin Piccadilly Line and know that our action must be on a number of fronts if we are to see aviation grow in a sustainable way."
Leo Murray, of the climate action group Plane Stupid, said: "The Government has finally said what we've know for years they were always going to say but the fact is that this runway cannot and will not be built.
"The Government can try and bulldoze over the opposition but we will stop this runway using every peaceful means at our disposal. Gordon Brown has obviously underestimated how many people are prepared to physically put themselves where they can't be ignored. Sipson will become the iconic battlefield of our generation and we will win."
Richard Lambert, director general of the CBI, said: "This approach to expanding Heathrow's capacity makes real sense. It will create the integrated transport system necessary for an economy that needs to grow in an environmentally sustainable fashion.
"We strongly support the tough environmental standards which have been proposed for the aviation industry - they are stretching but achievable. It's right that full use of the new runway capacity should be dependent on Heathrow meeting strict environmental requirements.
"Linking Heathrow to a high-speed rail network will increase the proportion of passengers who arrive by public transport and vastly improve connections to London and the rest of the UK.
"This is not an easy decision. But this announcement balances the needs of the economy with those of the environment, and provides the right framework for the country's long-term needs."
Labour MP, John McDonnell (Hayes and Harlington), whose constituency includes Heathrow airport, said the third runway was Labour's "new poll tax, with wings", adding: "The Government's announcement is not the end of the battle against the third runway, it is just the beginning.
"Opponents will use every mechanism possible to prevent the runway going ahead including campaigns in Parliament, in the courts, in the planning process, in the media and if necessary in direct action.
"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."
London's mayor Boris Johnson said: "This is a truly devastating blow for millions of Londoners whose lives are now set to be blighted by massive increases in air pollution and noise.
"The Government has singularly failed to deliver a convincing case for expansion throughout or adequate solutions for the nightmare problems this would cause.
"No amount of sweeteners in the shape of transport infrastructure will fundamentally alter the fact that the Government is hell-bent on exacerbating a planning error of the 1940s and that Heathrow is not fit for purpose.
"I am deeply concerned that the proper processes of coming to this decision may not have been followed, and will support a legal challenge should this prove to be the case. To this end we are currently considering today's announcement in detail.
"I throw down the gauntlet to Gordon Brown to publicly defend this deeply undemocratic decision on the 21st of January at my People's Question Time in Hillingdon - a community that is being asked to live with its consequences.
"There has never been a proper public debate on this issue and now the Government has decided to proceed, there clearly has to be."
Dr Mark Avery, conservation director of the RSPB, said: "This decision shows that the UK's policies on tackling climate change are a sham. The Government will never hit its carbon cuts targets if Heathrow has a third runway.
"No green sweeteners will compensate for the huge emissions that thousands of extra flights will produce no matter what claims are made for environmentally benign new planes."
Phil Thornhill, national co-ordinator of the Campaign against Climate Change, said: "In the face of an avalanche of scientific evidence that the dire threat from catastrophic climate change is more grave and more imminent than ever then to ignore that threat in major decisions such as Heathrow is the height of irresponsibility.
"Investment in green jobs and sustainable infrastructure should be the Government's priority to make this country fit for the future."
Bob Crow, leader of the Rail Maritime and Transport union, said: "Today's decision is a major setback, but the campaign for a sensible and sustainable alternative will go on.
"In the face of overwhelming evidence that rapid development of high-speed rail would make a third runway unnecessary, the Government has instead caved in to big-business.
"A high-speed rail network linking with Heathrow makes sense as part of a transport strategy that aims to reduce carbon emissions but, however it is dressed up, massive airport expansion will worsen pollution."
Greenpeace executive director John Sauven said: "This is Gordon's big Heathrow con. It is perhaps the most striking example of greenwash this country has ever seen. These proposals would make Heathrow the single biggest emitter of CO2 in the country and would be a disaster for the fight against climate change.
"Hoping for an aeroplane that doesn't cause global warming is like holding out for a cigarette that doesn't cause cancer. It's not going to happen, and the only way to deal with the problem is to reduce consumption. This new runway cannot and will not be built."
Mr Sauven added: "If Gordon Brown thinks this is a green runway then he must be colour-blind. This package is designed to patch up a cabinet split and will do very little to reduce the huge environmental impact of an expanded Heathrow, which will now become the single biggest emitter of carbon-dioxide in the country.
"These new emissions caps aren't even legally binding. The loopholes in this are so big you could fly a jumbo jet through them."
David Frost, director general of the British Chambers of Commerce, said: "This sends a strong message to the world that we are a nation open for business.
"We're pleased that the Government has recognised just how important expanding Heathrow is to the UK's future economic prospects.
"The decisions on airport expansion and high-speed rail will be absolutely critical in ensuring our country has the key infrastructure it needs to attract investment and drive our economy forward."
The Department for Energy and Climate Change welcomed the measures on tackling emissions from aviation, which had not even been on the table as recently as 10 days ago.
Officials at the department said the development of targets to cut emissions below 2005 levels by 2050, measures on "green slots" and limiting capacity made the UK the first country to acknowledge there could not be unconstrained airport expansion.
The department also believes the measures mean decisions on aviation expansion are in the hands of the Government's Committee on Climate Change, rather than BAA.
But conservation charity WWF-UK's chief executive David Nussbaum said the Government had failed "spectacularly" its first big test of credibility since the Climate Change Act with its targets to cut emissions came into force.
He warned: "Expanding airports will make it incredibly difficult and expensive for the UK to meet its carbon targets. Every other sector of the economy, from manufacturing to home heating to cars, will have to tighten its belt to allow the aviation sector to grow in this way.
And Benedict Southworth, director of the World Development Movement said: "Dubbing this climate killing project 'the green Heathrow' is the most dangerous greenwash of our times. It's like calling a new motorway 'green' because it has a cycle path.
"The aviation industry has just been given free rein to pollute while other sectors of industry and the British public will be forced to cut emissions."
Christian Aid warned the building of a third runway at Heathrow would be seen by many in the developing world as evidence rich countries would always put self-interest above tackling climate change.
The charity said the Government's decision undermined the UK's leadership in achieving an international deal on cutting emissions in Copenhagen this year.
But BAA chief executive Colin Matthews said: "This decision opens the door to Heathrow becoming a truly world class hub airport, and to the UK maintaining the direct connections to the rest of the world on which our prosperity depends.
"Meeting the environmental targets will be demanding, but, whilst we have to study the detail in today's announcement, we are determined to work with the rest of the aviation industry to achieve them.
"We are also fully aware that today's decision will be a difficult one for many, particularly those residents who will be directly affected by it.
"We intend to work with the local community as much as possible as we go through the planning process."
TUC general secretary Brendan Barber welcomed the decision, adding: "Aviation is key to the UK economy and will support the creation of many more quality jobs.
"But unions acknowledge the environmental concerns that many of us have raised, and are committed to supporting the sustainable development of Heathrow.
"We therefore expect the Government to hold to its commitments not to breach local noise and air quality standards, and ensure that CO2 emissions from aviation growth are consistent with the UK's new carbon budgets."
Miles Templeman, director general of the Institute of Directors, said: "With the current airport operating at 99% of capacity, Heathrow's status as a global hub is under threat.
"A third runway is vital to maintaining the UK's economic competitiveness, and will put us in a good position to win business from the key markets such as India and China when the upturn comes."Reuse content