Tory minister Greg Hands resigns from Theresa May's government in protest over Heathrow Airport expansion

Walkout piles pressure on Boris Johnson – who is expected to be out of the country to avoid having to vote on Monday

A government minister has dramatically resigned in protest at the expansion of Heathrow Airport, vowing to “honour” his pledge to fight the project.

Greg Hands, the trade minister, said he had no choice but to quit after Theresa May decided to whip Tory MPs to vote in favour of the third runway.

The resignation will pile pressure on Boris Johnson – the fiercest critic of the expansion – who is instead expected to be out of the country, to avoid having to vote on Monday.

It is also a big blow to the prime minister, because Mr Hands had been charged with piloting the vital trade bill through the Commons over the next few weeks.

In a tweet, Mr Hands said: “As the government will be whipping the vote on Monday, this means I am resigning from the government.

“I wrote to the PM earlier this week on how I will honour these 2017 general election pledges to the people of Chelsea and Fulham and vote against the Heathrow third runway on Monday.”

Pressure has been growing on Mr Johnson over Heathrow, after his celebrated pledge to protestors to “lie down with you in front of those bulldozers and stop the building, stop the construction of that third runway”.

Even since becoming foreign secretary, he has insisted expansion “will be stopped” – warning London faces a disastrous future as “the city of planes” if it goes ahead.

However, he is expected to miss Monday’s crucial vote by being at a meeting in Brussels, even though – with the vote not taking place until 10pm – he would appear to have time to return for it.

Labour used the resignation to turn the focus to Mr Johnson, with Andy McDonald, the shadow transport secretary, saying: “Boris Johnson promised his constituents he would ‘lie down in front of the bulldozers’ to stop a third runway.

“Instead he is jetting off to Luxembourg on Monday to avoid the vote because he is too weak to stand by his promises.”

The focus will also be on Philip Hammond, the chancellor, another minister with a seat under the Heathrow flightpath who has criticised expansion in the past.

However, Labour’s own position has been widely-ridiculed, after the party said the project failed key environmental and climate change tests – yet its own MPs would enjoy a free vote.

The party is split down the middle, with John McDonnell, the shadow chancellor fiercely opposed, but most northern and Scottish MPs in favour.

Heathrow bosses have so far refused to say which areas of the capital will be affected by hundreds of thousands more flights a year at the west London airport.

But many MPs in west London are facing huge pressure from constituents. Mr Hands won Chelsea and Fulham at last year’s election with a majority of 8,188.

Mr Johnson said in December 2016: “We are going to see an inevitable fight in the courts and I think the chances of success for the proponents of the third runway are not high.

“New York is going to be the city of beautiful skyscrapers, Paris the city of lights and London in the future, if we go ahead with this project, will be known as the city of planes.”

A Downing Street spokesman said: “Greg Hands has served the government with great ability and distinction over several years, and we thank him for all of his work.

“This government is committed to expanding airport capacity at Heathrow – this is an important decision which will play a crucial role in securing the future of global Britain.”