Boris Johnson has quit his role as Foreign Secretary as Theresa May’s government lurched towards its biggest crisis.

Last month the MP for Uxbridge and South Ruislip was criticised after missing a vote over a third runway at Heathrow - something he said he would always oppose.

However, he claimed he could no longer support Mrs May’s strategy for Brexit negotiations, following a meeting at the Prime Minister’s residence at Chequers last week.

In a terse statement, a Downing Street spokesperson said: "This afternoon, the Prime Minister accepted the resignation of Boris Johnson as Foreign Secretary. His replacement will be announced shortly. The Prime Minister thanks Boris for his work."

Mr Johnson’s position looked precarious following the decision of fellow Leave campaigner David Davies to step down as Brexit Secretary late last night.

There had been confusion over Mr Johnson's whereabouts all morning as Westminster’s rumour mill buzzed.

He was due to attend a Cobra briefing at the Cabinet Office - but his sizeable security detail remained outside his official residence at Carlton Gardens.

Officers twice warned journalists the Foreign Secretary was about to leave, only to then say they had been told to stand by.

However, it appears Downing Street released news of Mr Johnson's departure, while he was still writing his resignation note, which was finally made public shortly after 6pm.

And it made for difficult reading - a critical shot across the bows for Mrs May's government.

"Brexit should be about opportunity and hope. It should be a chance to do things differently, to be more nimble and dynamic and to maximise the particular advantages of the UK as an open, outward-looking global economy," wrote Mr Johnson.

"That dream is dying, suffocated by needlesss self-doubt."