A high-profile Conservative dramatically quit as the decision to build a third runway at Heathrow opened up another damaging rift within the Tory party.

Just a year after he was the Conservative candidate to become London mayor, Zac Goldsmith resigned as an MP in protest at his government’s choice.

The move triggers a by-election in his seat of Richmond Park, in which Mr Goldsmith is expected to stand on an anti-Heathrow ticket.

Mr Goldsmith warned that the decision would be a “millstone” around the government’s neck and declared the plan “undeliverable”.

That word were echoed by the Foreign Secretary Boris Johnson.

Both he and the Education Secretary, Justine Greening, who described the decision as “extremely disappointing”, have been given an unusual dispensation to attack the plan.

Normally cabinet members are bound by the convention of collective responsibility.

But Prime Minister Theresa May has decided to 'relax' the rule in a bid to prevent more resignations.

Mr Johnson predicted that the Heathrow decision, the biggest yet taken by Mrs May's government, is likely to be stopped.

The Foreign Secretary said the project would cause "inevitable degradation" to the quality of life of people under the potential new flight paths.

He added: "A third runway is undeliverable.

"The day when the bulldozers appear is a long way off, if indeed they ever materialise."

His own plan, for a new airport in the Thames Estuary, dubbed 'Boris Island', was a "better solution", he said.

He added: "No other great city would do this to its inhabitants. 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."

Mr Johnson anticipated the proposal would be "snarled up" in legal cases.

"I think it very likely it will be stopped," he said.

"We have been here before and 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."