Sir Keir Starmer has said he will stand down as the Labour MP for Holborn and St Pancras, a decision that will trigger a by-election in the north London seat he has held since 2015. The former prime minister announced the move on Tuesday in an interview with his local newspaper, the Camden New Journal, which reported it as an exclusive, and in a statement posted on X.

The vacancy will be the first electoral test for Andy Burnham's government, six weeks after he replaced Starmer in Downing Street. No poll date has been set: BBC News reported that a date will not be fixed until Starmer formally resigns his Commons seat, which he has not yet done.

"Over the summer, I have had time to reflect and consider my future. I have decided that now is the right time to step down as MP for Holborn and St Pancras and hand the baton over to a successor…" Starmer said in his statement.

He told the Camden New Journal he wanted to concentrate on work abroad. "I will now focus on other things and that will be international affairs including defence, security, trade and technology in a fast-changing world. I will also continue, as I have done for a long time now with others, work on combating violence against women and girls," he said, adding: "It's work I started before I became an MP and it's work I'm keen to continue after I'm an MP." He did not name a role, employer or organisation.

Of the seat itself, he said: "It has been a huge honour and privilege to represent the best constituency in the country and to have taken over from Frank Dobson, who was such a great constituency MP and a member of the last Labour government"

The paper reported that Starmer has informed local Labour constituency party staff, and that the party will now begin a selection process. Press Association copy said a timetable for selecting candidates is due to be announced in the coming weeks.

Starmer was prime minister from July 2024. He announced on 22 June this year that he would resign as Labour leader and prime minister; Burnham was acclaimed leader on 17 July and took office on 20 July, having returned to the Commons as MP for Makerfield at a by-election on 18 June.

Accounts differ on the commitment Starmer gave about his future as a backbencher. Press Association reported that after he left Downing Street, No 10 said he would stay on as an MP until the next general election, while BBC-derived copy said Starmer himself gave that undertaking in a BBC interview shortly after stepping down.

Kevin Hollinrake, the Conservative Party chairman, seized on that. "Whilst we have disagreed with almost all of Sir Keir Starmer's decisions, I wish him and his family well for the future," he said in a statement. "It is fitting that his final act as a Member of Parliament is yet another U-turn having pledged to stay on". He added that 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."

At the general election of 4 July 2024, Starmer held the seat with 18,884 votes, 48.9 per cent, a majority of 11,572 or 30 points on a turnout of 54.1 per cent, according to Parliament's official results record. His share was down 17.3 points on 2019.

The constituency has since shown movement. The Ham & High reported that the Holborn and Covent Garden ward, which sits inside the seat, was won by three Green candidates for the first time at Camden's local elections in May, defeating the Labour council leader, Richard Olszewski. The Guardian reported that the Green leader, Zack Polanski, a London Assembly member who does not sit in the Commons, is understood to be considering a run.

MPs cannot resign directly, and must instead be appointed to a nominal Crown office — the Chiltern Hundreds or the Manor of Northstead — to vacate a seat.