Britain's Labour government on Wednesday backed a plan for a third runway at London's busy Heathrow airport, with finance minister Rachel Reeves saying it would help grow the economy while respecting climate goals.

"I can confirm today that this government supports a third runway at Heathrow and is inviting proposals to be brought forward by the summer," Reeves said in a speech, adding that a new airstrip "would unlock growth".

Despite opposition from environmentalists and some Labour MPs, Prime Minister Keir Starmer is determined to deliver major infrastructure projects to grow a UK economy that has struggled to take off since the party came to power in July.