Johnson bowed to the inevitable after he was abandoned by ministers and MPs
He says process for choosing new leader should start now during speech outside Downing Street
Defence minister Ben Wallace emerges as early front-runner to lead Conservatives
Shailesh Vara has been appointed as the new Northern Ireland Secretary
Former Prime Minister John Major has written to the chairman of the Tory 1922 Committee to warn it is “unwise” for Boris Johnson to remain in office while his successor is chosen.
Mr Major also suggested either an interim premier or a streamlined election process would be “in the national interest”.
He intervened as scandal-ridden Johnson confirmed he will quit as British prime minister after he was abandoned by ministers and most of his Conservative MPs.
Bowing to the inevitable as more than 50 ministers quit and MPs said he must go, an isolated and powerless Johnson spoke outside Downing Street to confirm he would resign.
"The process of choosing that new leader should begin now. And today I have appointed a cabinet to serve, as I will until a new leader is in place," Johnson said during a speech outside Downing Street.
He added: “It is clearly now the will of the parliamentary Conservative Party that there should be a new leader of that party and therefore a new prime minister.
"And I've agreed with Sir Graham Brady, the chairman of our backbench MPs, that the process of choosing that new leader should begin now and the timetable will be announced next week.”
Johnson said it had been an "immense privilege" to serve as prime minister and thanked the British public as he concluded his speech.
He said: "Above all, I want to thank you, the British public, for the immense privilege that you have given me and I want you to know that from now on until the new prime minister is in place, your interests will be served and the Government of the country will carry on.
"Being Prime Minister is an education in itself. I have travelled to every part of the United Kingdom and in addition to the beauty of our natural world I have found so many people possessed of such boundless British originality and so willing to tackle old problems in news ways that I know that even if things seem dark now, our future together is golden.
"Thank you all very much. Thank you.
"I know that there will be many people who are relieved and perhaps quite a few who will also be disappointed. And I want you to know how sad I am to be giving up the best job in the world."
"But them's the breaks.”
After days of battling for his job, the scandal-plagued Johnson had been deserted by all but a handful of allies after the latest in a series of scandals broke their willingness to support him.
The Conservatives will now have to elect a new leader, a process which could take weeks or months.
Defence minister Ben Wallace has emerged as the early favourite among Conservative party members to be the next leader, according to a YouGov poll showed on Thursday, as Prime Minister Boris Johnson was expected to resign.
Scotland’s First Minister Nicola Sturgeon said there will be a "widespread sense of relief" as the Prime Minister prepares to stand down.
However, Ms Sturgeon questioned whether it is “sustainable” for Johnson to stay on in the role.
She wrote on Twitter: “There will be a widespread sense of relief that the chaos of the last few days (indeed months) will come to an end, though notion of Boris Johnson staying on as PM until autumn seems far from ideal, and surely not sustainable?"
She added that the Prime Minister was "manifestly unfit" to be Prime Minister, claiming that the events of this week shows the "Westminster system is broken".
Johnson’s decision to resign as Conservative Party leader followed another chaotic morning as recently-appointed chancellor Nadhim Zahawi told Boris Johnson this morning: “You must do the right thing and go now", as his refusal to accept that he has lost the trust of Conservative MPs has triggered another wave of ministerial resignations.
The Cabinet minister, who was only appointed to the role this week, tweeted an image of a letter with the caption; “Prime Minister: this is not sustainable and it will only get worse: for you, for the Conservative Party and most importantly of all the country. You must do the right thing and go now.”
Meanwhile, Brandon Lewis earlier quit his Cabinet post as Northern Ireland Secretary, telling the British Prime Minister the government requires “honesty, integrity and mutual respect” and it is “now past the point of no return”.
His departure was soon followed by a string of other ministers as the number of MPs quitting government and party posts since Tuesday evening topped 50.
Helen Whately quit as a Treasury minister, telling Mr Johnson: “I have argued that you should continue as Prime Minister many times in recent months, but there are only so many times you can apologise and move on. That point has been reached.”
Damian Hinds resigned as security minister, telling Mr Johnson there has been a “serious erosion” in standards in public life and “faith in our democracy and public administration”.
He said on Twitter: “It shouldn’t take the resignation of dozens of colleagues, but for our country, and trust in our democracy, we must have a change of leadership.”
Science minister George Freeman wrote to the Prime Minister to say he no longer has confidence in his leadership.
In his resignation letter, he told Mr Johnson “the chaos in your Cabinet and No 10 this month is destroying our credibility” and “it can’t go on”.
Guy Opperman left his role as pensions minister, telling Mr Johnson that “recent events have shown clearly that the Government simply cannot function with you in charge”.
Technology minister Chris Phiilp has also resigned this morning, saying the “PM should step down given public and Parliamentary confidence has clearly gone, and given the importance of integrity in public life”.
James Cartlidge has also quit as courts’ minister, telling Boris Johnson: “The position is clearly untenable.”
And Education Secretary Michelle Donelan resigned as well.
The departure of Mr Lewis meant four Cabinet ministers have quit – Simon Hart resigned as Welsh secretary on Wednesday night, while chancellor Rishi Sunak and health secretary Sajid Javid stepped down on Tuesday, triggering the leadership crisis.
Michael Gove was fired as communities secretary, with No 10 sources describing him as a “snake” who had briefed against Mr Johnson.
The point-blank refusal to accept the pleas of his own Cabinet ministers to quit was a stark difference to Margaret Thatcher, who agreed to step down after Cabinet pressure in 1990.
The stand-off was unlike anything in modern British political history, with Theresa May and Tony Blair having agreed to leave office after mounting criticism within their party in recent decades.
Priti Patel, the Home Secretary, Nadhim Zahawi, the Chancellor, and Chris Heaton-Harris, the Chief Whip, were among the Cabinet figures who told Mr Johnson he had lost the support of his party. More than half a dozen cabinet figures made that argument.
Simon Hart, the Welsh Secretary, and Brandon Lewis, the Northern Ireland Secretary, both were prepared to resign but held back to confront Mr Johnson. Last night they were both on resignation watch.
In total 42 Tory MPs resigned from official positions in the last 48 hours. That included 17 government ministers quitting, 14 yesterday.
Graham Brady, the 1922 Committee chairman, yesterday told Mr Johnson that a second vote on his leadership could happen as early as next week, with a new 1922 executive voted in place on Monday and free to change the leadership rules on Tuesday.
Not everyone in the Cabinet turned on Mr Johnson yesterday. Both Jacob Rees-Mogg, the Brexit minister, and Nadine Dorries, the Culture Secretary – two of Mr Johnson’s most loyal supporters – rushed to Number 10 to urge him to stay.
Figures close to cabinet ministers Liz Truss and Ben Wallace, who were travelling, declined to say whether they urged Mr Johnson privately to go.
Mr Zahawi also did not quit last night, despite warning the prime minister of the perilous political position. He was back in the Treasury and was working with Number 10 on a speech on a “new economic plan”, which will include tax cuts.
Mr Gove did tell Mr Johnson to resign. He held a five minute one-on-one meeting with the prime minister yesterday morning where he urged him to quit on his own terms before it was too late.
Downing Street critics pointed the finger at Mr Gove after four figures in his department quit yesterday afternoon, fuelling calls for Mr Johnson to go.
An ally of Mr Gove denied he was plotting and said he would “100 percent” not stand to be Tory leader if there was a contest.
Throughout the day a succession of ministers and parliamentary private secretaries resigned, many tweeting out letters with excoriating views of the prime minister.
Mr Johnson also had to endure two Tory MPs calling for him to go during Prime Minister’s Questions, after which he sat with his arms crossed as Sajid Javid, his former health secretary who quit on Tuesday, gave a speech in the Commons calling for the cabinet to act.
Yet during a two-hour grilling before the Liaison Committee, Mr Johnson declared he was having a “terrific” week and insisted his government was pushing ahead with “ever increasing energy”.
There were signs last night of the mass resignations making government difficult, with planned scrutiny of a piece of legislation with MPs cancelled because the minister in question had quit.