Andy Burnham has suggested that more flights could use Manchester Airport before Heathrow is allowed to expand.
The former Mayor of Greater Manchester has cast serious doubt over the plans for a third runway in west London, refusing five times to back the development.
He stressed at Labour’s annual conference in Liverpool that there was a “strong case” for a bigger Heathrow.
But he also argued that it might be better to make use of existing capacity at Manchester Airport before permitting the west London airport to expand.
Mr Burnham recently emphasised that key to whether his Government backs a third runway is the view of London.
Mayor Lord Sadiq Khan is strongly opposed to a bigger Heathrow.
However, the PM’s stance has faced a backlash from some union chiefs and he appeared to have amended his stance, now stressing that “it's such a decision of importance for the whole country”.
Grilled on a bigger Heathrow on LBC Radio, Mr Burnham said “I’m not saying that I've taken a position. You know, it's important that where there is a consultation, potentially a planning application, I need to handle that carefully.”
Pressed whether he was minded to support a new runway, he added: “Well, I'm on the record as saying that Heathrow could be a good idea. I have said that in the past.”
However, he added: “In my past role as Mayor of Greater Manchester, though, I looked at the second runway at Manchester, and it has capacity.
“So, I think we do need to have a wider discussion about what is the right airport configuration for the country in the long run, and where airports have got capacity, should that be used first before we allow further airport expansion.
“But I am on this one having to say that I am listening to both sides of the argument. There is a strong case for it...”
The PM’s latest intervention comes as the £49billion development, which airlines say would be the most expensive new runway project ever and would involve moving the M25, has already been hit with years of delays.
The new runway would increase the west London airport’s capacity to 756,000 flights and 150 million passengers a year.
The Government’s own global warming advisers have warned that there is “no credible pathway” for a Heathrow third runway within the UK’s legally-binding climate targets under current policies for cutting aviation emissions.
The UK’s Climate Change Committee also stressed that the Government “does not have a credible plan to reduce” aviation emissions, posing a serious challenge to meeting overall global warming targets.
Mr Burnham added: “There's been a consultation, and it's really important, given it's such a decision of importance for the whole country, to take time to see the outcome of the consultation.
“Obviously, Heathrow Airport is a huge economic driver for the country, but there are concerns and those need to be considered.”
His stance is at odds with that of his Chancellor John Healey who just weeks ago gave firm backing to expansion of the west London airport.
