LONDON — The U.K. Department for Transport released an appraisal of the proposed Heathrow third runway that calculated a net present value between -£23.4bn and -£62.5bn. The appraisal estimates represent the overall social value of expanding Heathrow compared with not expanding it. The department's documents also indicate the third runway is expected to boost gross domestic product by up to 0.05%, which is a 90% reduction from a previously cited government figure of 0.5%.

The appraisal attributes between £29bn and £42.4bn in positive benefits to passengers, primarily from lower air fares. It also projects that profits at airlines and other airports will decrease by approximately £25bn. The appraisal estimates the social and environmental impact of the runway at between £58bn and £82bn. An external analysis commissioned by the department found the scheme could add up to 0.05% to gross domestic product by 2056.

Alex Chapman, head of economic policy at the New Economics Foundation, said, "In its desperation for a fraction of a per cent of GDP growth, this government has lost its way. They said they were backing Heathrow expansion for economic reasons but their own analysis shows it won't deliver. The results from the department's impact assessment must be some of the worst in history, and reflect what we've been saying for the past year: the economic argument for expansion does not add up."

A department spokesperson said, "Net present value is just one part of the overall picture – crucially, an expanded Heathrow could support over 60,000 new local jobs and deliver £40bn of benefits to the UK. This will attract international investment and strengthen Britain's connectivity, and we have been clear that expansion will be financed by the private sector."

Heathrow stated the appraisal model excluded ways expansion could increase economic competitiveness and did not capture the value of UK trade. The proposed 3,500-metre runway would require diverting the M25 motorway and demolishing approximately 800 homes. A department health impact assessment found the third runway could harm the health and wellbeing of up to 3 million nearby residents.

Liberal Democrat transport spokesperson Olly Glover said, "Labour can't show how a Heathrow expansion squares with our climate commitments, or that it can be delivered anywhere near legal noise and air pollution limits. Real leadership delivers economic progress without trashing our climate commitments or steamrolling the communities in the flight path."