Sir Keir Starmer has announced he is quitting as MP for Holborn and St Pancras, setting off a by-election that Labour is expected to fight hard to keep, with the Green Party signalling it may contest the seat.
Starmer, who served as Prime Minister before stepping down in July, said it was the "right time" to leave the Commons and focus on international affairs, including defence, security, trade and technology. He also said he would continue working on combating violence against women and girls.
Holborn and St Pancras has been held by Labour for 43 years. Starmer was first elected in the spring of 2015, succeeding Frank Dobson, and in the 2024 general election, under slightly new boundaries, his majority was cut to just over 11,000.
The by-election will be a major test for Andy Burnham, who took over as Labour leader after Starmer stepped down as PM. The Greens, led by Zack Polanski, have made historic gains in London at May's local elections, seizing control of several councils from Labour.
Robert Ford, a politics professor at the University of Manchester, wrote on X: "The seat has exceptionally high shares of non-white voters (66 per cent), graduates (51 per cent) and young ppl (47 per cent aged 16-39) – all groups that have swung Lab to Green in recent years. This could be a humdinger of a by-election."
The Greens' challenge could be boosted by the independent candidate Andrew Feinstein, who came closest to beating Starmer in the last general election. Feinstein wrote on X: "We must ensure that all progressive forces in Holborn & St. Pancras unite in order to deliver an MP who represents us & will work for us" – which some see as a hint of a possible deal with the Greens to deny Labour victory.
Labour is briefing members that the by-election "could become a straight contest between Labour and the Greens."
The selection process for a new Labour candidate has already begun, with the party due to choose its candidate as soon as next Wednesday.
Starmer told the Camden New Journal: "It has been a huge honour and privilege to represent the best constituency in the country and to have taken over from Frank Dobson... I will now focus on other things and that will be international affairs including defence, security, trade and technology in a fast-changing world."
Andy Burnham paid tribute, saying Starmer "has given this country a lifetime of public service" and that his leadership took Labour from "one of its worst defeats" to one of "its best victories." Burnham added: "We will use it well and we wish his family the very best for the future."
Conservative Party chairman Kevin Hollinrake described the decision as "another U-turn" and said: "The decision to stand down will mean a costly by-election for taxpayers at a time when Andy Burnham and John Healey are plotting tax rises on hardworking families across the country. The Conservatives look forward to giving the people of Holborn and St Pancras a chance to vote for a stronger economy and a stronger country in the weeks ahead."
Kemi Badenoch, the Conservative leader, said she was surprised by the announcement, writing on X: "I was surprised to hear he was standing down from Parliament. But I can understand why he would not want to spend time with the Labour MPs who treated him so badly after he won them their seats."
Starmer informed local Labour constituency party staff of his decision to exit Parliament after 11 years representing the north London seat. He also pointed to Labour's 2024 election victory as a huge achievement.
The by-election is expected to be a closely watched contest, with the outcome potentially shaping the political landscape ahead of the next general election.