Boris Johnson has defended his decision to miss a crucial Commons vote on Heathrow expansion, saying his resignation from the Government would achieve “absolutely nothing”.

The Foreign Secretary faced widespread derision after he chose to be out of the country on official business on Monday despite his long-standing opposition to a third runway.

His absence meant he was able to avoid a choice between voting against Heathrow expansion on a three-line whip, which would have meant quitting as Foreign Secretary, or supporting the Government in order to keep his job.

In an open letter to constituents in his west London seat, quoted in the Evening Standard, he said: “My resignation would have achieved absolutely nothing.”

The Foreign Office confirmed Mr Johnson was travelling overseas, his destination was not announced in advance on “security grounds”.

“He is not in the country. He is travelling,” a spokeswoman said.

Jeremy Corbyn poured scorn on his decision to stay away, despite his Uxbridge and South Ruislip constituency lying under the Heathrow flight path and his past promise to “lie down in front of those bulldozers” to prevent expansion going ahead.

The Labour leader told the Press Association: “I would have thought, if nothing else, as a constituency MP he would want to be in the Commons because, after all, his constituency is very, very near to Heathrow, and he has in the past made very strong statements against Heathrow, and, indeed, once he promised to lie down in front of a bulldozer on it.

“But, he seems to be somewhere abroad, unknown destination, and nobody seems to be fully aware of where the Foreign Secretary is.

“And, I think we should be told.

“If he is unable to be present, then we have to ask the question what on earth is he doing and who is he representing?”

In his letter, Mr Johnson said he had been urged by local councillors  to carry on in office so that he could continue to oppose a third runway from within the Government.

Heathrow expansion
A plane landing at Heathrow Airport (Steve Parsons/PA)

“I have long been an opponent of a third runway at Heathrow and that is why I am not voting for it tonight.

“I have made clear my opposition since joining the Government, and I will continue to lobby colleagues from within government.

“Some of my critics have suggested that I should resign over the issue.

“No doubt they have my best interests at heart.

“But it is clear from what is likely to be a large majority of MPs who are in favour of a third runway that my resignation would have achieved absolutely nothing.

“Hillingdon council have been emphatic that they would rather have me in the Cabinet and fighting for their cause on this and other issues.”

He added: “On election night I promised with John McDonnell, the Labour MP, to lie in front of the bulldozers.

“In view of the very considerable difficulties that still face the third runway, its cost and the appalling air and noise pollution entailed
by the project, I believe it will be a very long time before we have to make good on that pledge; if indeed a third runway ever comes about.”

Mr Johnson’s decision to avoid the vote was thrown into sharp relief by his fellow west London MP Greg Hands who last week quit as international trade minister so he could honour an election pledge to vote against Heathrow expansion.

In a tweet on Sunday, Mr Hands wrote pointedly: “Great to arrive back in the UK at Luton Airport in time for the (England) match today and to vote against Heathrow expansion tomorrow.

Heathrow expansion
A plane lands at Heathrow (Steve Parsons/PA)

“I wouldn’t want to be abroad for either of those. #commitments.”

Speaking on BBC Radio 5 Live, Mr Hands said that he had never considered arranging to to be out of the country to avoid the vote.

“I was clear from the beginning, and made it clear from the beginning, that I would be voting against and that any option to be somewhere else was not going to be viable for me, because of the very clear pledge that I have made to my electors in Chelsea and Fulham, which could hardly have been clearer,” he said.

Other Tory MPs made clear they were unimpressed by Mr Johnson’s refusal took take a stand on an issue on which he had previously fought so strongly.

Conservative backbencher Sarah Wollaston told BBC Radio 4’s The Westminster Hour that Mr Johnson should have resigned “on a point of principle”.

“Just being conveniently out of the country I’m afraid won’t wash.

“I think this would be an opportunity for a colleague like Boris Johnson to actually put his money where his mouth is,” she said.

Former Welsh secretary Stephen Crabb said Mr Johnson would “need to look his constituents in the eye and explain where he was on the night of the Heathrow vote”.

When the Government originally announced its decision to go ahead with a third runway, Prime Minister Theresa May said ministers with long-standing objections they would be allowed to continue to oppose it at a local level but would not be permitted to speak out in Parliament.