Controversial plans to expand Heathrow airport have been approved by Cabinet ministers – as it emerged Boris Johnson will be allowed to duck a crunch Commons vote on the issue.

Theresa May and her senior ministers effectively gave the go ahead for a £14bn third runway in west London as they confirmed a new National [Airports] Policy Statement to grow the UK’s aviation capacity.

The move, confirmed to MPs by Transport Secretary Chris Grayling, follows decades of delay and bitter opposition from campaigners who claim the plan will lead to more noise, air pollution and undermine Britain’s climate change fight.

Foreign Secretary Johnson, who famously vowed to “lie down in front of the bulldozers” at the airport, is expected to be absent overseas – with permission – when the issue is put to a whipped vote before early July.

Under a relaxation of Cabinet collective responsibility rules, he will be given an exemption to speak out to continue his opposition to local media.

The Evening Standard later revealed that Johnson was the only Cabinet minister to express his opposition in the meeting on Tuesday morning.

HuffPost has learned that Labour has not ruled out refusing to ‘pair’ Johnson in the vote if he is abroad. 

The Opposition is furious over plans to ram a key Brexit bill through the Commons in one day next week and is tempted to break usual conventions which prevent ministerial absences affecting the balance of key votes.

The Prime Minister’s official spokesman stressed that the decision had legally and technically not been taken by the full Cabinet, but by a special Economy and Industrial Strategy (Airports) Sub-Committee.

The committee includes May, Grayling, Channellor Philip Hammond – but not Johnson.

It could be another 10 years before the new runway is built. But critics of the Tories point out that in 2009, David Cameron made a public pledge: “No ifs, no buts, no third runway”.

In his statement to MPs, Grayling said the approval was an “historic moment” and “the time for action is now”.

He stressed that the expansion would be financed with private not public money, and said that curbs on night flights would be strict.

Grayling said there would be up to £2.6bn made available “towards compensation, noise insulation and improvement to amenities” around the new runway, ten times more than offered under a 2009 scheme.

The focus will now switch to a possible knife-edge vote in the Commons, with several Tory rebels determined to oppose the plans.

Former Cabinet minister Justine Greening has appealed to SNP MPs to help block the plans, warning that it would divert much-needed cash away from Scotland towards London.

Greening, who is tipped to run against Sadiq Khan for the London Mayoralty in 2020, is vehemently against any extra runway at Heathrow. She told MPs Londoners’ lives would be “blighted”.

Labour has yet to decide if it will back the Heathrow expansion and has set four ‘tests’ on its impact on jobs across the country and its impact on the environment.

Shadow Transport Secretary Andy McDonald said that if the tests weren’t met, the courts would block the plans anyway.

McDonald said that Labour did not trust Grayling or the Government to deliver on its promises.

May and most of her Cabinet back the plans as a key part of building a ‘global Britain’ after Brexit, with enhanced airline passenger and freight links to the rest of the world.

Green MP Caroline Lucas said it was “outrageous” that the words “climate change” didn’t appear once in Grayling’s statement.

Jenny Bates, clean air campaigner at Friends of the Earth, said: “It’s depressingly ironic that the Cabinet gave the go-ahead to a third runway at Heathrow on World Environment Day.

“Heathrow expansion would be bad news for our climate and will bring more noise, air pollution and misery to local residents.”

But Unite, Britain’s biggest trade union, came out strongly for the expansion.

National officer Oliver Richardson said: “Ministers need to avoid playing parliamentary games with such an important project and put Heathrow expansion to a vote of MPs as soon as possible.

“The UK is a world leader in aviation and aerospace. We urge MPs from all political parties to back growth for the UK economy and vote for Heathrow’s expansion to create and maintain high quality jobs.”  

And the SNP announced that it would back the plans as they could secure up to 16,000 jobs in Scotland.