London's world-renowned reputation is at risk after the government backed a third runway at Heathrow Airport today (25 October), Boris Johnson has warned.

The foreign secretary claimed the UK capital could become known as the "city of planes" if the expansion of the West London site goes ahead.

"What I worry about is that down the line, if and when, a third runway were to be built (I don't think it would be) there would be overwhelming clamour to build a fourth runway as soon as it was completed, and then what would London be like?" Johnson told BBC News.

"You would have New York, a city of beautiful skyscrapers. Paris the 'city of lights' and London the 'city of planes'. Is that really what we want for our fantastic capital city?"

The former Mayor of London's comments came after Transport Secretary Chris Grayling confirmed to MPs that a cabinet sub-committee had backed expansion of Heathrow rather than Gatwick Airport.

"A new runway at Heathrow will improve connectivity in the UK itself and crucially boost our connections with the rest of the world, supporting exports, trade and job opportunities," Grayling said.

"This isn't just a great deal for business, it's a great deal for passengers who will also benefit from access to more airlines, destinations and flights."

The government has argued that the economic benefits to passengers and the wider economy are worth up to £61bn ($75bn) over 60 years.

The SNP also back the move, with Labour leader Jeremy Corbyn expected to give his MPs a free vote on the issue. But Labour's Mayor of London Sadiq Khan is opposed to a third runway at Heathrow.

Parliament is expected to have a vote in the winter of 2017/18. In the meantime, Number 10 has allowed Johnson and Education Secretary Justine Greening to express their "personal views" for a "limited time".

Ministers are usually expected to follow collective cabinet responsibility, which would stop Johnson and Greening protesting the decision.

Watch: Interview with Jonathan Bartley IBTimes UK

Green co-leader Jonathan Bartley has urged the Uxbridge and South Ruislip MP to quit Theresa May's top team.

"A free vote isn't enough, he will still be muzzled and he would still not be able to campaign against Heathrow expansion," Bartley told IBTimes UK.

"He's nailed his colours to the mast – he said he would campaign against it and the only way to do that is to resign."

Conservative MP Zac Goldsmith is expected to resign from the House of Commons over the decision. The former Mayor of London hopeful would trigger a by-election for the Richmond Park seat if he made such a move.

The environmentalist, who secured a majority of more than 23,000 at the general election, is expected to run as an independent candidate.