London Mayor Sadiq Khan has turned on his own party to condemn the Labour government's proposal to bid for the Olympics in the north of England.
Mr Khan insisted the north would 'fail to unleash' the Olympics' full potential, and it would be a 'missed opportunity' to snub the capital, which hosted the Games in 2012.
This rails against ministers, who have commissioned UK Sport to conduct an 'initial strategic assessment' into whether the region could be a host in the 2040s.
The funding agency is working to assess the possible costs and benefits of hosting the Games in the north, and whether a bid would have any chance of success.
Culture Secretary Lisa Nandy said the government was 'starting the firing gun' on the project.
But even at this preliminary stage, Mr Khan felt compelled to shoot down the proposal.
A spokesperson for the London mayor said: 'London is the sporting capital of the world and the Mayor has openly expressed his ambition for the capital to be part of a future Olympic and Paralympic Games.
'Sadiq believes that a potential country-wide bid, using all the assets we have in the UK, including the publicly-owned London Stadium would deliver the very best possible Olympics.
Sadiq Khan turned on the Labour government's proposal to consider bidding to host the Olympics in the north of England
Mr Khan intervention pitted him directly against Lisa Nandy, the Culture Secretary, who said it was 'time the Olympics came north'
'Using London's existing world-class infrastructure would help deliver the greenest and most sustainable Games, as well as unlocking huge economic growth both here in London and around the country.
'Not including the capital in an Olympics bid would be a missed opportunity, and mean our country fails to unleash the full benefits of a UK-wide games.'
Making the case for at least entertaining the idea of a northern bid, Ms Nandy earlier said: 'For too long we have been told the Olympics is simply too big and too important to be hosted in the north.
'Not any more. It's time the Olympics came north and we showed what we can offer to the world.
'We know that we can pull off the most incredible, not just bid, but Olympics. So we're kick-starting that with a phase-one study about the investment, the resources, the infrastructure, the transport that we're going to need.'
The findings of UK Sport's ongoing assessment will determine whether to proceed with the next stage of preparing a bid.
This would mean putting together a 'technical feasibility study', but the final decision on any bid would remain with the British Olympic Association (BOA).