Video report by ITV News Political Editor Robert Peston
Theresa May will fight any attempt to unseat her through a vote of no confidence by Conservative MPs, Downing Street has said, after her administration was thrown into further turmoil by the resignations of two Cabinet members.
Boris Johnson resigned as Foreign Secretary amid splits over Brexit, warning in his resignation letter that Britain appeared to be "heading for a semi-Brexit" and would take on "the status of a colony" under her plans.
His departure came just hours after former Brexit Secretary David Davis quit, saying he could not back and deliver the Government's plan as he does not believe in.
Jeremy Hunt has been named the new Foreign Secretary, leaving his post as Health Secretary which he has held since 2012.
Matt Hancock has been appointed Health Secretary in Hunt's place, with Jeremy Wright replacing him as Digital, Culture, Media and Sport Secretary.
Speaking in the House of Commons minutes after Johnson's resignation, Theresa May was loudly heckled as she rose to deliver a statement on the Cabinet's Chequers Brexit agreement.
Her attempt to pay tribute to her former Cabinet colleagues Boris Johnson and David Davis was met with jeers and laughter.
Some Labour MPs shouted "resign" while others waved "bye" as Mrs May took to the despatch box.
Watch in full: Theresa May's Brexit statement and questions in the Commons
Sterling fell sharply following news of the Cabinet resignations.
ITV News Political Editor Robert Peston says Johnson and Davis resigned because they "hate" May's Brexit plans, and see them as a "betrayal of the referendum vote".
He added that the PM has never been under more pressure in the Commons than she was today.
The plan agreed at Chequers will see the UK take EU rules for how it produces goods and food, and will also see Britain collect tariffs on behalf of Europe.
Due to this, the European Court of Justice (ECJ) will still hold some sway in the UK, all of which Mr Johnson and Mr Davis see as breaches of what the British people thought they were voting for in the referendum.
Before delivering the statement to the Commons, the Prime Minister said she wanted to "pay tribute to my right honourable friends... for their work over the past two years".
Mrs May continued that while she, Johnson, and Davis "do not agree about" the best way to proceed with Brexit, she thanked the former Brexit secretary for the work he did on steering through some of the "most important legislation for generations".
While she said she wanted to "recognise the passion" that the outgoing foreign secretary had shown in promoting a "global Britain to the world".
Labour leader Jeremy Corbyn told the Commons in reply: "We are two years on from the referendum - two years of soundbites, indecision and Cabinet infighting, culminating in a series of wasted opportunities with more and more people losing faith that this Government is capable of delivering a good Brexit deal.
"And that is just within her own Cabinet."
He added: "There are now only a few months left until these negotiations are supposed to conclude. We have a crisis in Government, two secretaries of state have resigned and still we are no clearer on what the future relationship with our nearest neighbours and biggest partners will look like.
Jeremy Corbyn and Theresa May exchange jibes over front bench resignations
"Workers and businesses deserve better than this," Corbyn continued.
"It is clear... this Government is not capable of securing a deal to protect the economy, jobs and living standards. This Government cannot secure a good deal for Britain."
May, in her reply, criticised Corbyn for initially saying in 2016 that Article 50 should have been triggered immediately after the EU referendum.
She said: "He talks about resignations - can I just remind him, I think he's had 103 resignations from his frontbench, so I'll take no lectures from him."
May claimed Labour would "never deliver" a strong economy, adding the Opposition's policies would lead to a "run on the pound, capital flight and the loss of jobs for working people up and down this country".
Davis has been replaced by former housing minister Dominic Raab.
Johnson backed Mrs May's Brexit plan at Chequers on Friday, despite reportedly claiming that defending the plans during the meeting was like “polishing a turd”.
There was growing speculation about the 54-year-old's plans on Monday after he failed to attend a meeting of the Government's Cobra emergencies committee as well as a summit of Western Balkan nations being held in London.
President of the European Council Donald Tusk said on Monday the "mess caused by Brexit is the biggest problem in the history of EU-UK relations".