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.

Shadow transport secretary Theresa May said: "What the British people and the airport industry want is certainty for the future of aviation. Now, they have been condemned to uncertainty.

"Airport expansion is an extremely important issue and we are glad the government is making an announcement on this matter. However, 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."

Transport spokesman John Thurso said: "The government have finally adopted the Liberal Democrat approach to the future of the aviation industry and accepted our long term policies of ending 'predict and provide' and introducing the 'polluter pays' concept to the aviation industry. These are long standing Liberal Democrat policies and their adoption by government comes not a moment too soon.

"However the government have completely fudged the details of how these policies will be introduced. There is a clear gap between the acceptance of our position on aviation and their actual implementation by a government discredited on transport and environmental policy."

Forum Response: Virgin Atlantic

Sir Richard Branson, chairman of Virgin Atlantic, said: "Alistair Darling has shown real courage in taking the tough decision to opt for at least two runways and in particular to include Heathrow within his plans for airport expansion over the next three decades.

"Had Heathrow not been included in the White Paper its pre-eminence in European and World aviation would have been lost, leading to the loss of thousands of jobs to other European airports.

"Unlike his predecessors the secretary of transport hasn't bottled the big decision and Britain will gain from his belief that the benefits of aviation's expansion can be achieved with environmental sustainability.

"I am confident that the environmental challenges accompanying expansion can and will be overcome. To avoid being overtaken by the rest of Europe we now need to move quickly in order to ensure that the new runway at Heathrow is operational as soon as possible after 2015.

"We are pleased that the government has taken the decision to safeguard land for the possible future development of Gatwick. In the meantime, before new runways are built, it makes environmental sense to make the maximum use of our existing capacity by introducing mixed-mode operations at Heathrow.

"In this respect, secretary of state's announcement that there should be a public consultation on mixed-mode is welcome, but we urge all the parties concerned to undertake this as soon as possible.

"We remain totally opposed to cross-subsidisation between London airports. We look to the independent regulator, the Civil Aviation Authority, to maintain its current position that those who should benefit from Stansted should pay for its development."

Forum Response: Strategic Aviation Special Interest Group

Councillor Richard Worrall, chairman of SASIG, said: "I think the government has said there is no change in the policy that has been followed for the last 30 years - the aviation industry should bring forward and justify their proposals and, as before we, the government probably won't say no.

"I believe the government has missed the opportunity of a lifetime for both British business and British travellers. Whereas most people are saying what they don't want, SASIG has consistently argued for the best solution for the country.

"It is sad that the government lacks the courage and flair to do what is right."

Forum Response: Institute of Directors

A spokesman for the IoD said: "Runway expansion is of great importance to the economic well-being of the South East.

"An additional runway is vital if the region is to compete with its continental competitors. Precisely which airport was chosen for expansion was always going to be a difficult decision to make, however it was a decision that had to be made, and we are therefore pleased with today's announcement from the transport secretary."

Forum Response: Woodland Trust

Ed Pomfret, senior public affairs officer at the Woodland Trust, told ePolitix.com: "The government is ignoring its own conservation policies and is conveniently forgetting its commitments to protect ancient woodland (land continuously wooded for at least 4000 years).

"If we really are to have a sustainable aviation policy we must manage demand to ensure that we don't damage this irreplaceable habitat. The proposals in the white paper reveal fundamental flaws in government thinking about sustainable development and climate change.

"Ancient woodland must be protected from these destructive plans. The proposals would destroy large areas of ancient woodland at Stansted, Birmingham and Manchester and we are also concerned that Gatwick has not been ruled out completely.

"Climate change is the biggest threat to biodiversity and the survival of ancient woods. Aviation makes a significant contribution to greenhouse gas emissions that cause climate change and demand must be managed to ensure that damage to our environment is reduced.

"We have maintained sustained, long-term opposition to all airport expansion proposals that threaten ancient woodland. Most recently, on Tuesday 9 December, Peter Ainsworth MP presented a petition to parliament on behalf of the Trust that thousands of opponents of airport expansion signed.

"In support of planned expansion at Stansted the government has already approved other massive housing development in the area which will cause even further loss and damage to irreplaceable woods and trees. The South East's green lungs are being concreted over. Radical preventative medicine is needed immediately."

Forum Response: GMB

Charlie King, civil aviation policy spokesman for the GMB, said: "The government's balanced response to the increased demands in the aviation industry is good for jobs, the economy and the regions.

"It will create thousands of jobs directly and indirectly across the UK and increase regional and international access. Alistair Darling has effectively balanced environmental concerns with the need to expand capacity across the country.

"Though the GMB is disappointed that the new runway at Heathrow may be delayed, we are confident that Heathrow will be able to meet the criteria earlier than 2015 and should get the green light as soon as they have."

Forum Response: National Trust

Tony Burton, director of policy and strategy at the National Trust, said: "The White Paper is based on an assumption that the demand for air travel will accelerate.

"Yet, continuing to pump prime the market for artificially cheap leisure flights - which comprise 74 per cent of all flights - makes no sense when the result is widespread damage to the country's environment and to its domestic tourism industry.

"The White Paper does not go nearly far enough to create more sustainable market conditions or to reflect the true costs that aviation puts on the environment and the rest of the economy.

"The appalling damage about to be inflicted on Hatfield Forest and the countryside around Stansted is just one example of the price we will all soon be paying for the failure of the government's aviation policy to address rising demand.

"The White Paper is an inadequate, short-sighted and unsustainable policy response to the rising demand for air travel. The result of this misguided approach will be enormous economic damage and the loss of some of our best loved environments.

"The government needs to think again or its plans will face the severest of opposition through the planning system when their real impact becomes apparent on the ground".

Forum Response: Corporation of London

Michael Snyder, chairman of the Corporation of London's Policy and Resources Committee, said: "The government's commitment to airport expansion is excellent news for the City.

"London's competitive edge as the world's leading international financial and business centre is dependent upon a strong and effective transport system, of which air travel is playing an increasing part.

"The expansion at Heathrow in particular is essential as it provides the vital hub to Europe, the US and Asia's growing economic markets. The planned work and consultation needs to be completed swiftly so that the Heathrow timetable will be met."