Theresa May’s £14 billion plan to extend Heathrow has been cleared for take-off, helped by more than 100 Labour MPs backing the move in a Commons vote as the SNP was accused of “letting Scotland down” after it decided to abstain.

Following a four-hour debate, MPs voted overwhelmingly to back the third runway: 415 to 119; a majority of 296.

Chris Grayling, the Transport Secretary, said the endorsement of the UK Government’s National Airports Policy Statement was a "really important step for our nation," and would move matters on from decades of debate to set a “clear path to our future as a global nation in the post-Brexit world".

But Andy McDonald, his Labour shadow, made clear the proposal failed to meet his party’s tests on environmental safeguards and regional connectivity and John McDonnell, the Shadow Chancellor whose London constituency would be affected by expansion, warned how villages, which had existed for 1,000 years, would be "wiped off the face of the earth" by Heathrow expansion to enable a company to maximise its profits.

READ MORE: Boris Johnson defends missing Heathrow vote

Yet while Labour opposed the expansion plan, it allowed its MPs a free vote.

Some 119 voted with the Government and 94 for the party’s official policy of opposing it, which helped to give Theresa May and her colleagues a decisive victory.

Carolyn Fairbairn, Director-General of the CBI, welcomed the decision, saying: “Fifty years in the making, this is a truly historic decision that will open the doors to a new era in the UK’s global trading relationships.”

David Mundell, the Scottish Secretary, hailed the vote as a "boost for the whole of Scotland".

But Greenpeace UK made clear the battle for Heathrow was not over as it announced it was ready to join a cross-party group of London councils and Sadiq Khan, the city’s mayor, to mount a legal challenge against the third runway plan.

At one point during the debate Central lobby at Westminster was locked down after 12 demonstrators from Vote No Heathrow staged a "lie-in" in protest at the Heathrow expansion plans.

As mooted, the Nationalist leadership decided to order its MPs to abstain, a decision which was said to have angered some SNP backbenchers given the Scottish Government had previously come out enthusiastically for Heathrow expansion.

READ MORE: SNP accused of putting party interests before national interests by abstaining on Heathrow vote

Edinburgh had said a third runway offered the “greatest strategic and economic benefits to Scotland,” creating up to 16,000 jobs and providing a significant boost to the nation’s air connectivity.

Last week, the UK Government claimed a third runway would result in 100 new weekly flights between Scotland and Heathrow; reserved slots for Scotland flights and new competition on existing routes, which could lead to lower prices for passengers.

But Alan Brown, the SNP’s transport spokesman, insisted Whitehall had failed to give sufficient guarantees.

“I want to see the jobs come to Scotland, I want to see a logistics hub at Prestwick and I want to see regional airport connectivity but, crucially, I want these aspects guaranteed. This is where the UK Government has fallen short,” insisted the MP for Kilmarnock and Loudoun.

At one point, Mr Grayling intervened to point out how Heathrow had now agreed with the Scottish Government to double the extra flight slots a third runway would bring to Scotland - to 200.

Mr Brown accepted 200 was better than 100 but again insisted he wanted to see the UK Government provide the guarantees.

Ian Blackford, the party leader, said when the slots were divided up between Scotland’s airports, there was not enough. “It’s the UK Government that has not stood up to protect Scotland’s interests; that’s the point,” he declared.

But Mr Grayling suggested the SNP’s position was that because it was unsure how big a slice of the Heathrow cake Scotland would get, “there should be no cake”.

His colleague at the Department for Transport, Jesse Norman, branded the Nationalists’ abstentionist position as “frankly risible”.

Outwith the chamber, Luke Graham, the Scottish Conservative MP, hit out at the Nationalists’ abstention, saying: "Heathrow expansion will bring huge benefits to Scotland yet the SNP have ignored that to pursue their agenda of disruption at Westminster.”

The MP for Ochil and South Perthshire added: “They have put their Nationalist interests before the national interest and they should be ashamed.”

His Tory colleague, Ross Thomson, who represents Aberdeen South, also hit out, saying the SNP was “letting Scotland and Aberdeen down”.

During the Commons exchanges shouts of "Where's Boris?" were heard as one notable absentee in the debate was Boris Johnson, who, it emerged, was 3,500 miles away in Afghanistan.

READ MORE: Scotland would secure 100 extra flights with London if third Heathrow runway green lit

The Foreign Secretary, whose Uxbridge constituency lies under the Heathrow flight-path, once famously said he would lie down in front of the bulldozers to prevent the airport being extended.

But yesterday he was conveniently abroad, talking to Afghan Government ministers in Kabul. In a letter to constituents, Mr Johnson defended his decision not to resign over the matter, declaring: "My resignation would have achieved absolutely nothing."

But Labour denounced the Foreign Secretary as “spineless,” saying his decision to absent himself to save his job proved he was “utterly devoid of courage, strength or principle”.