Labour is facing a challenge from the Greens to succeed Sir Keir Starmer as MP for Holborn and St Pancras.
Former Prime Minister Sir Keir announced on September 1 that he is standing down as an MP, triggering a crunch by-election battle in the north London constituency.
Sir Keir has been the MP for Holborn and St Pancras since 2015 and was elected Prime Minister in 2024.
He left Downing Street in , following the election of Andy Burnham as the new Labour Party leader.
Speaking to the Camden New Journal, following weeks of speculation as to whether he would remain an MP, Sir Keir said that the "time is right" to "pass the baton" to a new MP.
He added: “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 seat of Holborn and St Pancras was created in 1983, and has only ever been held by Labour.
Speaking in the Commons for the first time since becoming Prime Minister, Mr Burnham paid tribute to Sir Keir, saying his predecessor had "given this country a lifetime of public service".
When will the by-election be to replace Sir Keir Starmer?
Camden Council has confirmed that the Holborn and St Pancras by-election will be held on Thursday, October 8.
The process of triggering the by-election started with Labour’s Chief Whip Anneliese Midgley “moving the writ”.
This entailed a motion in the House of Commons chamber asking MPs to agree to issue a new election to replace the outgoing MP.
Speaker Sir Lindsay Hoyle then put the question to MPs to decide whether to agree to the motion.
As it was backed by MPs, the motion became an Order for the Speaker, who in turn issues a Warrant to the Clerk of the Crown who then sends the writ to the Returning Officer.
By-elections have to be held between 21 and 27 working days from the issuing of the writ.
Sir Keir will leave the House of Commons once a new MP has been elected to replace him.
When will we know the result?
The count will begin after polling stations close at 10pm on Thursday, October 10.
The result of by-elections usually are announced in the early hours of the morning the following day.
In 2024, the result in the General Election vote in Holborn and St Pancras was announced at 4.15am.
The time we know the result of the by-election will be influenced by the size of the turnout. The turnout in 2024 was 54.1%.
The last two by-elections in the UK saw turnouts of 44.1% (in Clacton on August 13, 2026, when Nigel Farage regained his seat), and 58.8% (in Makerfield on June 18, 2026, when Prime Minister Andy Burnham was elected MP).
