He said it has “rarely been more important for this country to stand by our allies, strengthen our partnerships and make sure our voice is heard”.

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Cameron will stick with the government’s existing approach to global challenges, including China and the conflict in the Middle East, Sunak’s spokesman said on Monday.

“Clearly, the prime minister and foreign secretary are aligned in our approach to the Israel-Gaza conflict,” the spokesman told reporters.

Asked if there would be any change on the British approach to China, the spokesman said: “We will continue with our consistent approach towards China.”

Cameron’s appointment was a massive shock in Westminster, not just because of the return of a former prime minister to government – the first since Alec Douglas-Home in the 1970s – but also because of his views on China.

During the Cameron administration there was a “golden era” of UK-China cooperation, something Sunak described as “naive” last year following growing tensions with Beijing

Cameron’s appointment on Monday came as a surprise to seasoned politics-watchers. It is rare for a non-lawmaker to take a senior government post, and it has been decades since a former prime minister held a Cabinet job.

Cameron has also been critical of Sunak’s decision to scrap the northern leg of the HS2 high-speed rail project, while the prime minister used his Conservative Party conference speech to distance himself from the legacy of his predecessors.

But the former prime minister made it clear he backs Sunak and will work with him to help the Conservatives win the general election, which is expected next year.

The new foreign secretary said: “Though I may have disagreed with some individual decisions, it is clear to me that Rishi Sunak is a strong and capable prime minister, who is showing exemplary leadership at a difficult time.”

The government said Cameron, seen walking into Downing Street as Sunak began his reshuffling, will be appointed to parliament’s unelected upper chamber, the House of Lords.

Sunak sacked Home Secretary Suella Braverman after she criticised the police’s handling of a pro-Palestinian march, with James Cleverly named the new home secretary.

Braverman had published an article in a newspaper on Thursday accusing the police of adopting “double standards” in their treatment of protests, an argument opposition Labour said inflamed tensions at the pro-Palestinian demonstration in London two days later.

The article was not cleared by Downing Street, the BBC said, and it emerged that Braverman had defied a request to tone her words down.

Under fire from opposition lawmakers and members of his own governing Conservative Party to eject her, Sunak moved against Braverman on Monday, asking her “to leave government” which she had accepted, a source said.

More than 140 people were arrested on Saturday after far-right counter protesters skirmished with police officers, who tried to keep them away from the 300,000 pro-Palestinian marchers.

Braverman was blamed for drawing out far-right groups that clashed with officers.

Also on Monday, British environment minister Therese Coffey resigned, she said in a letter to Sunak. Steve Barclay, who was health secretary, replaced her, while Victoria Atkins, formerly financial secretary to the Treasury, became the new health secretary.

Atkins will assume oversight of the National Health Service (NHS), Britain’s state-funded health system that is under pressure from industrial action by health workers and a growing list of patients waiting for treatment.

There are currently around 7.8 million people waiting for NHS treatment, a record high, compared to about 7 million a year ago.

One of Sunak’s top five priorities is to cut the waiting lists, although he has all but conceded it will now not happen this year, blaming months of industrial action for throwing progress off track

Sunak’s reshuffle was the latest reset for a prime minister whose party is badly lagging behind the Labour Party before an election expected next year.

Blow for Sunak as UK Tories suffer two damaging by-election losses

The return of Cameron suggested Sunak wanted to bring in a more centrist, experienced hand rather than appease the right of his party, which supported Braverman.

It also reawakens divisive debate over Brexit. Cameron held the referendum on European Union membership in 2016 and was hated by many in the Conservative Party after he campaigned to remain.

Pro-Brexit MP Jacob Rees-Mogg questioned whether Cameron’s appointment will antagonise some Conservative voters and push more of them to the right-wing Reform party.

Additional reporting by Bloomberg, Associated Press