The United Kingdom lawmaker on course to become the country's next prime minister in the coming days has said he wants his time in office to work as a "circuit-breaker" for the nation.

Andy Burnham, who was mayor of the English city of Manchester before launching his leadership challenge by securing election as a lawmaker on June 18, said in his first big speech since then that he plans to deliver "good growth in every postcode" of the UK and "across every nation and region".

The charismatic former Cabinet minister has long been a popular Labour Party politician but left Parliament in 2017 to focus on regional politics.

Burnham, who describes himself as a socialist and who is widely seen as part of the ruling Labour Party's soft left, was lured back into national politics after the party did poorly in local elections in May, which prompted criticism of Prime Minister Keir Starmer and his leadership style.

Starmer initially said he would resist any leadership challenge, but after resignations from his government, he has since announced his intention to step down once a replacement is found.