Senior government figures believe Starmer could outline both his resignation and a timetable for handing power to a successor after spending the weekend at Chequers considering his future amid growing pressure from within the Labour Party.
US President Donald Trump on Sunday went off the rails by declaring Starmer's impending exit. Trump framed Starmer's expected departure as a consequence of what he described as failures on immigration and energy policy, particularly Labour's stance on North Sea oil production.
"Keir Starmer will resign as Prime Minister of the UK. He has failed badly on two very important subjects: IMMIGRATION and ENERGY (OPEN UP THE NORTH SEA OIL!). I wish him all the best," he posted on Truth Social.
If Starmer steps down, Britain would be on the verge of welcoming its fifth prime minister in just four years, continuing a period of extraordinary political instability that has seen a succession of leaders leave office before completing a full parliamentary term.
Starmer entered Number 10 Downing Street following Labour's landslide victory in the July 2024 general election, ending 14 years of Conservative rule. He promised economic renewal, stronger public services and lower living costs, but his premiership has been increasingly overshadowed by internal party divisions and declining public support.
Pressure on the prime minister intensified after Labour suffered severe losses in local elections earlier this year, surrendering nearly 1,500 council seats in England, losing control of Wales and recording its worst-ever performance in elections to the Scottish Parliament.
Discontent within Labour had been growing even before those results. Critics accused Starmer of repeatedly changing course on major policy commitments, while his decision to appoint Lord Peter Mandelson as Britain's ambassador to the United States sparked controversy after renewed scrutiny of Mandelson's past association with convicted sex offender Jeffrey Epstein.
The political momentum shifted dramatically last week when Andy Burnham won the Makerfield by-election, returning to Parliament after nine years as Mayor of Greater Manchester.
Burnham increased Labour's majority in the constituency and defeated a strong challenge from Reform UK, providing a rare electoral success for Labour during a difficult period.
Burnham, who represented Leigh in Parliament from 2001 to 2017 and served in several Cabinet positions under previous Labour governments, has long been viewed as a potential national leader.
He unsuccessfully contested the Labour leadership in both 2010 and 2015 but has remained one of the party's most recognisable figures outside Westminster.
His return to Parliament was carefully orchestrated after former Makerfield MP Josh Simons stepped aside to allow Burnham to contest the seat, a move widely interpreted as creating a pathway for a future leadership challenge.
Burnham is expected to be sworn in as an MP on Monday afternoon. While a formal Labour leadership contest remains possible, many observers believe a "coronation" is increasingly likely if Starmer confirms his departure, with Burnham emerging as the overwhelming favourite to succeed him.
The prospect of another prime ministerial resignation inevitably recalls Britain's recent period of leadership turbulence.
In July 2022, then-Prime Minister Boris Johnson announced his resignation after a wave of ministerial departures and scandals that undermined his authority. He remained in office until a Conservative leadership contest elected his successor.
Johnson was followed by Liz Truss, whose premiership lasted just 49 days before she resigned in October 2022 after market turmoil triggered by her government's economic plans. Her departure made her the shortest-serving prime minister in British history.
Truss was succeeded by Rishi Sunak, who led the Conservatives until their defeat in the 2024 general election, when Starmer entered Downing Street as Labour leader.
Should Burnham ultimately replace Starmer without a general election, opposition parties are expected to question whether the new prime minister possesses a direct electoral mandate from voters.
A change of leadership would also usher in a new Cabinet and potentially a significantly revised policy agenda as Labour seeks to restore public confidence before the next national vote.
For now, Westminster awaits Starmer's decision, with the future direction of Britain's government potentially set to become clearer within hours.