Boris Johnson is coming under pressure to quit the cabinet over next week’s crucial vote on a third runway at Heathrow.

The Foreign Secretary once vowed to 'lie down in front of bulldozers’ if another runway at the airport next to his Uxbridge constituency was approved.

He was due to be out of the country when Monday’s crucial vote is held, meaning he could stay in Government but still deliver on his campaign promise that he would never back the third runaway.

International trade minister Greg Hands has already quit his position to vote against the Government, underlining his pledge to vote in Chelsea and Fulham voters at last year’s General Election.

And now attention is turning to Mr Johnson, who Labour has challenged to 'stand by his principles’.

Mr Johnson was due to be a Luxembourg for a meeting with EU foreign ministers but his deputy Alan Duncan will now attend that event on Monday.

And that puts the former London mayor in a tight political spot.

READ MORE: Boris reminded of bulldozers pledge as Heathrow vote nears 

“It’s one rule for Johnson and another for junior Minister Hands on Heathrow,” said Labour MP Ben Bradshaw. "Johnson can miss the vote, Hands must resign. That stinks."

When elected to his Uxbridge and South Ruislip constituency - where he commands a 5,034 majority - Mr Johnson used his acceptance speech to make a firm pledge on Heathrow.

He has previously condemned the third runway at Heathrow as a ‘disaster’. And also called the expansion plans ‘desperately short-sighted’ and ‘barbarically contemptuous of the rights of the population’, putting their health at risk.