Following the audience with the King, Burnham will return to Downing Street to deliver his first speech as prime minister. He is expected to pledge to give Britain "more breathing room" while promising a more "stable and responsible" approach to politics after years of political upheaval.

Burnham's appointment comes just days after he was elected Labour leader on Friday, triggering a rapid leadership transition at the top of government.

His arrival in Downing Street is expected to usher in a new policy agenda, with several key proposals already signalled. 

Among the measures being discussed is the possibility of an income tax cut, alongside broader plans aimed at easing pressure on households and restoring confidence in government.

Conservative Party leader Kemi Badenoch congratulated Burnham on taking office but questioned whether he was prepared for the role.

"I wish the new PM every success," Badenoch said, while warning that he was beginning his premiership without a "clear plan."

Burnham assumed office at a time of continued political instability in Britain. By midday Monday, the country will have had five prime ministers in just four years, underlining one of the most turbulent periods in modern British politics.