International Trade Minister Greg Hands MP has quit position over plans for the expansion of Heathrow Airport.
Hands said he was standing down after it was made clear that Tory MPs would not have a free vote in Monday’s Commons debate.
“As the Government will be whipping the vote on Monday, this means I am resigning from the Government,” he wrote on Twitter.
The MP for Chelsea and Fulham said he had written to Theresa May explaining that he intended to honour a pledge to his constituents at last year’s general election to vote against a third runway at Heathrow.
Mr Hands’s announcement throws the spotlight on to Foreign Secretary Boris Johnson, who has been a long-standing opponent of Heathrow expansion.
The vote coincides with a meeting of EU foreign ministers which could provide an excuse for him to stay away, although it is not known whether he will be at the gathering in Luxembourg.
Officials said the expansion of Heathrow would create 114,000 extra jobs in the area around the airport by 2030.
Aviation minister Baroness Sugg said: “A third runway at Heathrow would bring benefits of up to £74 billion to passengers and the wider economy, creating tens of thousands of local jobs in the process.
“It is easy to take these benefits for granted but our latest illustration, showing expansion would create enough jobs to fill well over 600 passenger jets, spells out just what MPs will be voting for.
“This massive project will bring fantastic opportunities for UK businesses, workers and apprentices and we cannot afford to wait any longer to push ahead with it.”
The Government also signalled it would make sure the extra capacity helped protect domestic routes.
Public service obligations would protect routes if required, which would also exempt them from air passenger duty.
Lady Sugg said: “About 15% of the new capacity will be used for flights to destinations within the UK or crown dependencies.”