UK finance minister Sajid Javid resigns amid UK government reshuffle
Johnson had asked Javid to fire and replace all of his special advisers, British media reported.
Rishi Sunak has been appointed Chancellor of the Exchequer to replace Javid, the prime minister's office said. Sunak is 39-years-old and the youngest person to hold the post.
He was first elected as a member of parliament in 2015. His father-in-law is the founder of tech company Infosys.
Foreign secretary Dominic Raab, de-facto deputy prime minister Michael Gove, home secretary Priti Patel, and justice minister Robert Buckland will keep their current positions.
Over the course of the day, Johnson sacked a number of his ministers.
Julian Smith, the Secretary of State for Northern Ireland, was one of the first ministers to be sacked in a surprise move that comes weeks after he brokered a deal to bring the province's government back after years of deadlock.
"Serving the people of Northern Ireland has been the greatest privilege," he tweeted. He had reportedly wanted to remain in the job.
Ireland's foreign minister tweeted that Smith had been "effective" at a time of "real challenge & risk".
"Without your leadership, I don’t believe NI would have a Govt today," Coveney added.
U have been such an effective SOS for NI at a time of real challenge & risk. Without your leadership I don’t believe NI would have a Govt today. Thank you @JulianSmithUK for your trust, friendship and courage; UK & #Ireland can look to future with more confidence because of it.— Simon Coveney (@simoncoveney) February 13, 2020
One Northern Irish MP tweeted: "Sacking the most successful SoS in a decade shows Johnson's dangerous indifference to us."
Taoiseach Leo Varadkar called Smith "one of Britain’s finest politicians".
Attorney General Geoffrey Cox, also sacked, said that as he returns to the backbenches, he will continue to support the prime minister. Cox had been scheduled to give questions in the House of Commons but was sacked.
Business secretary Andrea Leadsom lost her post as business secretary and said it was a "real privilege to serve in Government for the last six years".
She will be replaced by Alok Sharma. Sharma had previously been international development secretary. He was first elected to parliament in 2010.
Multiple ministers leave government
Universities and science minister Chris Skidmore said he would be spending more time with his family due to a "promotion in the reshuffle". It was not immediately clear if he had been sacked or not.
"Got a promotion in the #reshuffle to be a better Dad with more time to spend with this gorgeous little one," he tweeted.
Transport minister Nusrat Ghani said it had been a huge privilege to serve her role, though it is unclear if she was sacked or not.
"What the Prime Minister giveth, the Prime Minister taketh away: just over six months ago, I was delighted to be invited by the Prime Minister to return to government after three years on the backbenches. This morning he told me that I need to make way for someone new," former environment secretary Theresa Villiers wrote after being sacked.
Some ministers are expected to return to cabinet in new roles - Johnson announced for instance that he would assign a new minister to manage the high-speed rail project he greenlit on Monday.