British Prime Minister Keir Starmer announced his resignation on Monday after facing intense pressure following the political rise of Labour rival Andy Burnham. Starmer's departure will make him the sixth UK prime minister in a decade to leave office before completing a full term, highlighting the political instability that has persisted since the Brexit vote in 2016.Kier Starmer says he will resign as British PM on July 9 and the next PM will be picked by September. (Reuters)Starmer said he would remain as caretaker Prime Minister until Labour selects a new leader in the coming weeks.Track UK PM news LIVEHe has led Britain since Labour's landslide victory in the July 2024 general election. However, both his personal approval ratings and the party's popularity have declined sharply during his two years in office.Delivering a brief statement from 10 Downing Street to announce his departure, Starmer appeared emotional, with his voice breaking toward the end of his remarks.“The question my party is asking now is whether I am best placed to lead us into the next general election,” Starmer said. “I have heard the answer of my parliamentary party to that question, and I accept that answer with good grace.”Timeline to pick the new PMThe process to replace Starmer will begin with his formal resignation on July 9, the date he said he would step down as prime minister and Labour leader.The announcement came after a difficult weekend for Starmer, who reportedly reflected on his future following Burnham's victory in a special parliamentary election, said a Reuters report. Burnham, the former Labour mayor of Greater Manchester, had campaigned with the aim of challenging Starmer's leadership of both the party and the country.On June 22, Burnham is due to be sworn in as a Member of Parliament, further strengthening his position within Labour and setting the stage for a leadership contest, according to Reuters.Following Starmer's exit, Labour is expected to choose a new leader over the summer. Starmer said a successor would be in place by the time Parliament returns from its summer recess in September, ensuring a new prime minister is installed before lawmakers resume business.US President Donald Trump had predicted about the annoucement on Sunday even before Starmer's made it official today."Keir Starmer will resign as Prime Minister of The United Kingdom. He failed badly on two very important subjects- IMMIGRATION AND ENERGY (OPEN NORTH SEA OIL!). I wish him well! President DJT," Trump posted on his social media platform.