The letter, published in Britain's Sunday Telegraph newspaper, is signed by large corporations such as Microsoft Corp (MSFT.O) and Telefonica O2 (TEF.MC), and puts further pressure on the government to re-think its aviation policy.

The letter was also signed by Simon Walker, director-general of the Institute of Directors, and John Longworth, director general of the British Chambers of Commerce.

Heathrow is operating at almost full capacity after Britain's Conservative-led coalition government blocked development of a third runway when it came to power in 2010, as further expansion of the west London site would mean a huge increase in the number of planes flying directly over the capital.

Britain's Department for Transport (DfT) said it did not support the development of a third runway at Heathrow because of the "unacceptable environmental consequences."

"The government will consult on an overarching sustainable framework for UK aviation this spring and alongside this we will publish a call for evidence on maintaining effective UK hub airport connectivity," a DfT spokesman said.

"As the Chancellor made clear in his Autumn Statement, we will explore all the options for maintaining the UK's aviation hub status with the exception of a third runway at Heathrow."

Heathrow's operator, Ferrovial (FER.MC)-owned BAA, last month said Heathrow was falling behind rival European airports in the battle for lucrative routes to China because of the constraints on growth at Britain's largest airport.

Earlier this year British business group London First called on the government, which recently announced plans to hold a formal consultation on proposals for a Thames estuary hub, criticised the government for ruling out a third runway at Heathrow for political reasons.

(Reporting by Rhys Jones and Avril Ormsby; Editing by David Holmes)

• A Permanent Economic Emergency