Heathrow third runway: David Cameron warned over expansion delay by Labour affiliate Unite

General secretary Len McCluskey says the third runway is 'crucial to securing our country's long-term economic prosperity'

Protesters hold signs during a rally against a third runway at Heathrow airport, in Parliament Square (Getty)

The country’s largest trade union has urged David Cameron to approve the third runway at Heathrow airport.

Labour-affiliated Unite has co-signed a letter from several leading business groups - including the British Chambers of Commerce, London First, the Federation of Small Business and its fellow union the TUC - which said the third runway was “fundamental” to the success of the economy.

The cabinet is due to decide on the issue this week with several senior Conservative figures - whose south-eastern constituencies are likely to be affected - reportedly urging the Prime Minister to reconsider.

Unite’s support for the plans is at odds with the Labour leadership.

Shadow chancellor John McDonnell has campaigned vigorously against the move which will affect his Hayes and Harlington constituency in Greater London.

Jeremy Corbyn opposes the third runway on environmental grounds (Getty Images)

He is supported by Jeremy Corbyn, who opposes the expansion on environmental grounds.

Unite general secretary Len McCluskey said: "The building of a third runway is fundamental to the success of at least two major industries of strategic national importance, aviation and aerospace, as well as being crucial to securing our country's long-term economic prosperity.

"Over the coming decades the noise impacts of Heathrow are forecast to reduce significantly, as new and quieter aircraft come into service and as flight paths are redesigned and improved.

"With expansion, the overall number of flights would grow, but new approach and departure paths could enable the noise impacts to be dispersed more widely, limiting the impacts on any individual community."

He said measures like a ban on night flights, noise reduction guidelines and a guarantee to keep air quality within EU limits would minimise disruption to the local community.

Additional reporting by PA