UK politician Andy Burnham.

UK leader Keir Starmer announced his resignation on Monday following months of pressure, kickstarting a process that will see Britain get its seventh prime minister in a decade.

Veteran politician Andy Burnham, who secured a return to parliament just last week, appeared poised to succeed Starmer after would-be rival Wes Streeting offered him his support.

Starmer's voice cracking during an emotional speech outside 10 Downing Street, as he conceded he had lost the support of his Labour party MPs after just two years in office.

He said he had informed head of state King Charles III of his decision to resign so that a new Labour leader, and therefore prime minister, could be elected.