The candidates to become Labour's nomination for London mayor have clashed over airport expansion in their first hustings debate.

Tooting MP Sadiq Khan defended his opposition to a third runway at Heathrow, saying London's air quality was already breaching EU regulations.

He said Gatwick Airport should be expanded, with "high speed links" between the two and a single check-in.

But rival David Lammy accused him of "the same Ed Miliband politics".

"My view is the way to proceed is no third runway at Heathrow," Mr Khan said, calling for "a better Heathrow, not a bigger one".

'Gridlocked'

But Tottenham MP Mr Lammy questioned the timing of Mr Khan's decision, which came after the emergence of Conservative MP and environmental campaigner Zac Goldsmith as a potential Tory candidate for the 2016 election.

"Zac Goldsmith has announced he's running and suddenly Sadiq is against it," he said, accusing Mr Khan of "playing the same Ed Miliband politics that got us nowhere".

Former culture secretary Tessa Jowell said she was prepared to wait until the final report of the Airports Commission which is looking at the options for expanding London's air capacity before making up her mind.

But she warned against the issue becoming "gridlocked" in government.

Mansion tax

"We can't go on forever putting this decision off because it's just too difficult," she said.

Journalist Christian Wolmar said climate change should inform the decision, while Harrow West MP Gareth Thomas said new runways should be built at both Heathrow and Gatwick.

Hackney North and Stoke Newington MP Diane Abbott also opposed Heathrow expansion.

The candidates were also asked about the "mansion" tax on homes worth over £2m that was proposed by Labour ahead of the general election.

Mr Lammy, Ms Jowell, Ms Abbott and Mr Wolmar all criticised the policy, with Ms Jowell saying that while it had been "well intentioned" it had been "emblematically disastrous" for Labour because it had caused people "anxiety" even if they weren't affected.

Labour's mayoral line-up