Former British prime minister David Cameron has returned to government as the UK's new foreign minister, as part of a ministerial reshuffle, which also saw Suella Braverman sacked as home secretary.
A Downing Street source said Mr Sunak "asked Suella Braverman to leave government and she has accepted".
Mr Cameron was seen entering Downing Street before the reshuffle was announced.
Return of Cameron knocks Braverman departure off news agenda
Speaking after his appointment was confirmed, Mr Cameron said he hopes his experience will assist him in helping the Prime Minister to meet the vital challenges in foreign affairs.
He said while he may have disagreed with some individual decisions, "it is clear to me that Rishi Sunak is a strong and capable prime minister".
Mr Cameron added: "We are facing a daunting set of international challenges, including the war in Ukraine and the crisis in the Middle East".
James Cleverly, who was the UK's foreign minister, has been appointed as the new Home Secretary.
The Conservatives said Mr Sunak is carrying out a wider reshuffle which "strengthens his team in Government to deliver long-term decisions for a brighter future".
However, sacking one of the leading figures on the Tory right could pose difficulties for the Prime Minister as he seeks to get his party united behind him and ready for a general election expected next year.
Mr Sunak had come under growing pressure to remove Ms Braverman, an outspoken right-winger, after critics accused her of heightening tensions during weeks of contentious pro-Palestinian demonstrations and counter-protests in Britain.
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Following her dismissal, Ms Braverman said "it has been the greatest privilege of my life to serve as home secretary".
"I will have more to say in due course," she added.
This is Mr Sunak's first ministerial reshuffle since becoming prime minister last year.
"Here we go," the party said on X.
"Today @RishiSunak strengthens his team in government to deliver long-term decisions for a brighter future. Stay tuned for the latest."
🚨 HERE WE GO
— Conservatives (@Conservatives) November 13, 2023
Today @RishiSunak strengthens his team in Government to deliver long-term decisions for a brighter future.
Stay tuned for the latest. pic.twitter.com/ianN6edyDU
News of Mrs Braverman's exit came as defence minister James Heappey was touring broadcast studios.
Minutes before she was sacked, he had told LBC that Mr Sunak and his team in No 10 had been "very clear she (Mrs Braverman) has his confidence and, in that sense, one would imagine that she will continue".
But he was told on air during an ITV Good Morning Britain interview that she had been sacked, leaving him to say: "Your viewers will be enjoying my discomfort, but it is in this case difficult to offer commentary when I just don’t know what is going on."
Liberal Democrat leader Ed Davey said: "Suella Braverman was never fit to be Home Secretary. Rishi Sunak knew this and he still appointed her.
"It was the Prime Minister’s sheer cowardice that kept her in the job even for this long. We are witnessing a broken party and a broken Government, both of which are breaking this country."
Cameron to avoid regular questioning by MPs as Foreign Secretary
Mr Cameron, who was also made a peer, will escape having to face regular grillings by MPs because of his position in the House of Lords.
He will not face the regular sessions of Foreign Office questions, with more junior ministers instead fielding questions in the Commons chamber.
Shadow foreign secretary David Lammy criticised the situation, which will also mean that major statements are either made first in the Upper Chamber by Lord Cameron or by a less senior minister in the Commons.
Mr Lammy said that during an "international crisis", Mri Sunak "has chosen an unelected failure from the past who MPs cannot even hold to account".
Mr Cameron will face questions from elected MPs only when he appears before select committees.
The Institute for Government's senior researcher Dr Alice Lilly said it was "highly unusual" for secretaries of state to serve in the Lords - the last was Baroness Morgan as culture secretary as an interim measure in 2019-20 - and it is more than 40 years since a foreign secretary was in the upper chamber.
During Gordon Brown’s administration, two peers Peter Mandelson and Andrew Adonis served as business and transport secretaries respectively.
"After Adonis and Mandelson, the Lords put in place procedures to ensure that Secretaries of State in the Lords would have to answer questions in the Lords in the same way that they would do in the Commons, so I expect that will happen again," Dr Lilly said.
"And obviously there are plenty of other ministers in the Foreign Office who will be able to answer MPs’ questions, so it’s not like there will be nothing, but it won’t be direct from the Foreign Secretary."
She added that the culture of the Lords is "very different" from the Commons.
"It tends to be less overtly political; getting the right tone matters. Scrutiny is often of a high quality, because of the range and amount of experience that many members of the Lords have."
