Alistair Darling has announced plans to expand the UK's airport capacity but has warned that environmental concerns could restrict future growth.

The transport secretary said he supported a wide range of moves to add capacity to regions around the UK.

But he confirmed that a second runway should be built at Stansted "as soon as possible" and set out plans for a third runway at Heathrow.

Darling said pressure on airports in the South East "was more severe than in any other parts of the country".

He also announced further expansion of Manchester, Edinburgh, Bristol and other regional airports.

"The challenge we face is to deal with the pressures caused by the increasing need to travel whilst at the same time meeting our commitment to protect the environment in which we live," he said.

"Our economy depends on air travel. Many businesses, in both manufacturing and service industries, rely on air travel; and it is particularly important for many of the fastest growing sectors of the economy."

Whilst he called for airport operators to make the "best possible use of existing runways", Darling conceded two further runways would be needed over the next 30 years.

The minister admitted that the moves would have "significant" consequences but warned that Britain's future economic prosperity lay in meeting the increased demand.

To meet the predicted growth he said a second runway should be built at Stansted by 2012 - but pledged to adhere to "strict environmental controls".

He said there was a "strong case" for expansion at the Essex airport.

But he also conceded that Heathrow would need to expand if it is to retain its international role.

"In the South East, there are particular environmental concerns about expansion at the main London airports, but balanced against this there is the importance of these airports to the South East and to the UK's prosperity," he said.

"Failure to provide some additional capacity could have substantial repercussions in the country as a whole, as well as for us individually."

Darling admitted, however, that the problems of noise and nitrogen dioxide emissions would have to be tackled before a third runway could be considered at London's major airport.

And he pledged to put in place a "programme of action to prepare for increased capacity".

The transport secretary promised to legislate to strengthen measures to control noise pollution - ahead of moves to create the new runway soon after 2015.

He said the government would introduce higher charges on more polluting aircraft and introduce "stringent noise controls".

But he went on to warn that "building more and more capacity is simply not sustainable"

He said the government had a duty to balance the benefits of air travel "against the serious environmental impacts of air travel".

Shadow transport secretary Theresa May slammed the government's indecision on the issue of future air capacity.

"What the British people and the airport industry want is certainty for the future of aviation. Now, they have been condemned to uncertainty," she told MPs.

"The inconsistent manner in which the government has handled this exercise demonstrates real incompetence and lack of judgement.

"The proposals for Stansted come at the same time as John Prescott's plans to build thousands of more houses on the M11 Stansted corridor - another example of inconsistency in the government's thinking.

"The failure to consider how each area will cope with the increased volume of transport and the impact that expansion might have on the environment shows that the government have failed to demonstrate the joined-up thinking that they promised."

John Thurso, Liberal Democrat transport spokesman, said ministers had a duty to the environment.

''People's freedom to fly must be balanced against other people's freedom to enjoy a quiet life, get a good nights' sleep and breathe clean air," he said.

The announcement is also likely to come under fire from air operators, who believe there is an immediate need for additional capacity at Heathrow.

British Airways has warned that Stansted is the wrong location for additional capacity.

Unions also warned that ministers had a duty to preserve jobs in the British air industry.

"Getting the balance right between jobs and the environment is important," said TGWU general secretary Tony Woodley.

"But we can get it right if we accept that we looking to lead in the aviation world rather than follow."

The CBI welcomed the government's decision to expand Heathrow and urged Darling to press ahead quickly.

"We are hugely relieved that the government has accepted the overwhelming economic case for expansion at Heathrow," said Digby Jones.

"Failure to expand our global hub airport would hit business competitiveness, regional air services and economic development right across the country.

"It would have been disastrous if the government had simply kicked the tough decisions into the long grass."

Local airport activists have also warned they will fight the government's plans.

Plans to build a new runway at Stansted will be challenged by local residents.

"The government's green credentials are now totally discredited by this white paper whose clear message is to hell with protecting the environment, our national heritage and local communities: planes take priority," said Stop Stansted Expansion chairman Norman Mead.

And Lord Hanningfield, leader of Essex County Council, criticised plans for a new runway at Stansted as "unwanted and unworkable".

"If central government thinks that Stansted is the site of least resistance they will soon be disabused of that notion. We will be consulting lawyers over coming days to examine the possibility of mounting a legal challenge to this proposal," he said.

Environmentalists meanwhile are demanding fresh measures to curb the predicted explosion in air travel.

Friends of the Earth called on ministers to introduce a "congestion charge" on airlines.

The group says the move would allow the government to invest up to £9 billion in public and sustainable transport, including high-speed rail and safe school routes and would also "make new runways unnecessary at Stansted or Heathrow".