By Ed Conway, economics editor
None of Britain's other airports will be able to have major expansions in the coming decades if Heathrow gets its third runway, the government's adviser has warned.
John Gummer (Lord Deben), chair of the Committee on Climate Change (CCC), told Sky News that Heathrow's expansion would use up the majority of the envelope the aviation industry would have between now and 2050, implying that other expansions should not be permitted if Britain is to hit its climate targets.
The intervention comes only weeks after the government pledged to reduce its greenhouse gas emissions to zero in net terms by 2050.
Lord Deben said that there was nothing in that target to stop the expansion of Heathrow, but it would have knock-on consequences for the rest of the aviation sector, which is expected to keep creating greenhouse gases in future decades since carbon-neutral plane engines are still thought to be a long way off.
"If Heathrow is built it has to be built within the envelope of emissions which we have allowed for aviation," he said, adding: "It has knock-on effects. It means you can't build similar things elsewhere in the country.
"You're not going to be able to have expansions of a different kind elsewhere. You can't have [Heathrow's third runway] and other things.
"It is for the government to decide what we as a nation put our priorities in. But it has to realise that it can't move outside those parameters."
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The warning is significant, since the government has historically followed the recommendations laid down by the CCC, its official adviser on climate change.
MPs approved the Heathrow expansion, though that was without the knowledge that it might have prevented expansions at other airports, particularly those in Scotland and the north of England.
Jim O'Neill, the former Treasury minister who masterminded the previous government's Northern Powerhouse campaign, said the revelation raised questions about the scope for economic ambition at other potential sites for airport expansion.
"It's slightly depressing. because it locks in no real regional ambition.
"That framework is a sign of the lack of real big picture thinking of the art of the do-able in terms of both re-balancing and actually positioning Global Britain around the world."