London Mayor Sadiq Khan has warned he may take legal action against the UK government over its revived plans to build a third runway at Heathrow, citing serious concerns over air pollution, noise, and climate commitments. Khan doubled down on his longstanding opposition to Heathrow expansion, stating that the new runway would have a “severe impact” on Londoners and undermine Britain’s climate goals.
The plan, which Heathrow says could cost up to £49 billion including terminals and infrastructure, aims to secure planning approval by 2029 and become operational within a decade. The runway itself is now estimated to cost £21 billion, up from £14 billion in 2018 due to construction inflation.
Sadiq Khan: Runway Will Damage Public Health and Climate Targets
Khan said he would “carefully scrutinise” the proposed expansion and warned of a “huge knock-on effect” on London’s transport infrastructure. “I remain opposed to a new runway at Heathrow because of the severe impact it will have in terms of noise, air pollution, and meeting our climate change targets,” he said. “I remain unconvinced that you can deliver hundreds of thousands of additional flights every year without a hugely detrimental impact on our environment.”
He added that all options, including legal action, are on the table if the government proceeds.
Government Insists Expansion Is Vital for Economic Growth
Chancellor Rachel Reeves defended the third runway, calling it “essential” to the UK’s economic growth and international trade. “Airport expansion is essential if we’re going to seize the opportunities of being an open trading economy,” she said during a visit to Scotland. Reeves highlighted that Scottish exports such as salmon and whisky rely on Heathrow’s capacity and argued that expansion will include vital upgrades to infrastructure, including the M25.
Despite her “huge respect” for Khan, Reeves insisted the third runway would move forward and dismissed legal threats as likely to fail.
Labour Party Split Over Heathrow Expansion
The Heathrow third runway plan has reignited tensions within the Labour Party. While Transport Secretary Heidi Alexander welcomed the proposals as a step toward job creation and growth, other key figures remain opposed. Greater Manchester Mayor Andy Burnham has warned it could further centralise economic power in London, while Energy Secretary Ed Miliband has long opposed the expansion. Even Prime Minister Keir Starmer previously voted against the plan.
The government has also conditionally approved Gatwick Airport’s expansion, which involves increasing traffic and reconfiguring its standby runway for regular use—part of a broader pro-growth agenda that critics say could come at the expense of environmental commitments.
