London — British Prime Minister Keir Starmer announced Monday that he was resigning from his position as the leader of the ruling Labour Party, which will also see him replaced as the country's leader.

Starmer has been under mounting pressure to resign for weeks, and his decision came after a political rival from within Labour, former Manchester Mayor Andy Burnham, made it clear that he would challenge the prime minister for his job. 

Starmer had vowed to stay in his post, but his position became untenable as more and more Labour Party colleagues concluded his time was up. The timetable for his departure sped up after Burnham left his role as mayor and then won a seat last week as a Member of Parliament for his local constituency — a necessary move as prime ministers have long been chosen from among sitting members of the House of Commons.

It marks the end of a tumultuous reign for Starmer less than two years after his Labour Party was swept to power in a resounding national election victory — and less than two months after voters made their frustration with his handling of national affairs clear in a round of local elections. 

In a statement delivered outside his office and official residence at 10 Downing Street in London, Starmer extolled the virtues of his time in office, then added: 

"The question my party is asking now is whether I am best placed to lead us into the next election. I have heard the answer… and I accept that answer with good grace. Every decision I have made has been about putting the country first."

"I will resign as leader of the Labour Party," he said.

Starmer appeared to choke up toward the end of his remarks as he spoke of his children, whom he called his "pride and joy."  

This breaking news story will be updated.