Net Zero Secretary Ed Miliband has said he will not resign if the government backs a third runway at Heathrow following years of opposition by him.
In 2009, Mr Miliband threatened to resign from Gordon Brown's cabinet as energy and climate change secretary over plans for a new runway and in 2018 he said an expansion was "very likely" to make air pollution worse.
But he has now said the government can meet both its growth and net zero missions together.
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Asked if he will consider resigning if the government approves a third runway, he said: "Don't be ridiculous, no."
Chancellor Rachel Reeves is expected to use a speech next week to support the expansion, as well as at Gatwick and Luton.
Mr Miliband said the government's position is for any aviation expansion to take place within the UK's carbon budgets, which are part of plans to meet the country's 2050 target of reducing emissions by 100% compared with 1990 levels.
Independent advisers on the government's Climate Change Committee (CC) have called for no net airport expansion without a proper national plan to curb emissions from the aviation sector and manage passenger capacity.
Mr Miliband added: "What the Climate Change Committee says is that we've got to make sure any decisions we make on aviation including expansion take place within our carbon budgets.
"And they are 100% right about that and that's absolutely the position of the government.
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"We believe that we can meet our growth mission - our number one priority - and keep within carbon budgets and indeed that our clean energy mission is crucial and a central part of meeting our growth mission.
"Far from them being in contradiction, they are absolutely complimentary."
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He refused to say whether the country could still reach net zero if Heathrow gets a third runway.
"I'm not getting into speculation about specific issues like that.
"What I'm saying is that aviation is part of our economic growth and it has to take place within our carbon budgets, and that is accepted right across government because we have legally binding carbon budgets."
Ms Reeves dropped a heavy hint on Thursday at the World Economic Forum in Davos, Switzerland, that she intends to dismiss climate concerns and back Heathrow, Gatwick and Luton expansions as she said "growth is the number one mission of this government".
Mayor of London Sir Sadiq Khan stood his ground after winning a third term last year promising to oppose London airport expansions.
Mr Khan has this morning reiterated his opposition to the plans, telling the London Assembly the aviation sector is important for growth "but we face a climate crisis and a climate emergency".
"I'm quite clear, my views on the expansion of Heathrow by a new runway haven't changed," he said.
He added that if speculation about a new runway abiding by carbon targets, and concerns around noise and air pollution became a reality "we'll of course consider the merits of that case".
His spokesman told Sky News: "The mayor has a long-standing opposition to airport expansion around London - linked to the negative impact on air quality, noise, and London's ability to reach net zero by 2030."