It comes as the PM today sacked Suella Braverman as Home Secretary after she was accused of fuelling Armistice Day tensions by slamming Met Police chiefs.
A No 10 source said the Prime Minister "asked Suella Braverman to leave Government and she has accepted".
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".
Over the weekend, Ms Braverman came out swinging after growing calls for her to quit.
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But today she said: "It has been the greatest privilege of my life to serve as home secretary."
She added: "I will have more to say in due course."
Foreign Secretary James Cleverly was seen entering No 10 following news of Mrs Braverman’s exit.
The departing Foreign Secretary is the first appointment in a sweeping shake-up of his top team by the PM currently underway.
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's 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 Sir Ed Davey said: "Suella Braverman was never fit to be Home Secretary. Rishi Sunak knew this and he still appointed her.
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"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."