Sir Keir Starmer has resigned as the Labour MP for Holborn and St Pancras, triggering a by-election which could provide an early electoral test for his successor as Prime Minister, Andy Burnham.
The former prime minister announced the decision on Tuesday, 1 September 2026, as Parliament returned from its summer recess and Mr Burnham prepared to make his first appearance at the Commons despatch box as Prime Minister.
Sir Keir had previously indicated that he intended to remain on Labour’s back benches until the next general election. In a statement, however, he said he had concluded that “now is the right time” to step down.
He said he would turn his attention to “international affairs including defence, security, trade and technology in a fast-changing world”. His resignation was formally completed after the Treasury appointed him Steward and Bailiff of the Three Hundreds of Chiltern, one of the traditional offices used to enable MPs to vacate their seats.
The decision presents an immediate political challenge for Mr Burnham, who faces defending a London constituency that Labour has represented for decades but where its support has come under pressure.
Green Party weighs challenge in Holborn and St Pancras
Zack Polanski, the Green Party leader, is expected to consider standing for election in the seat. A party spokesperson said Mr Polanski had “always made it clear he would like to be a London MP” and that the capital had been his home for more than 20 years.
Mr Polanski said in April that he would “almost certainly” contest a future by-election in London, including Holborn and St Pancras if Sir Keir left Parliament. He also suggested in June that he could co-operate with, or enter a coalition with, a Labour government led by Mr Burnham.
The Greens are hoping to build on their gains in London’s local elections, where Labour suffered a substantial loss of support. The constituency’s electorate includes large numbers of young people, graduates and voters from ethnic minority backgrounds — groups that have increasingly moved away from Labour in recent contests.
At the 2024 general election, Sir Keir retained the seat with 18,884 votes, giving him a majority of 11,572. Independent candidate Andrew Feinstein finished second with 7,312 votes, while the Green candidate polled 4,030.
Luke Tryl, director of polling organisation More in Common, said the contest would test whether Mr Burnham could unite the left in a real election and protect Labour’s urban strongholds. For the Greens, he said, it would show whether Mr Polanski could regain the momentum built earlier in the year.
Professor Robert Ford of the University of Manchester described the contest as potentially a “humdinger of a by-election”, pointing to the seat’s high proportions of non-white voters, graduates and younger residents.
Mr Feinstein has also suggested that progressive candidates should work together to prevent a Labour victory. He said Holborn and St Pancras needed an MP who represented local residents and was “the antithesis of everything that Starmer stands for”.
The by-election is also expected to feature candidates from the right. Nigel Farage has confirmed that Reform UK will contest the seat, while Rupert Lowe has said his Restore Britain party will also stand.
