The by-election to replace former Labour MP Andrew Gwynne is likely to take place at the end of February, after the process to hold the poll was begun.
On Monday, government chief whip Jonathan Reynolds asked for the writ for the Gorton and Denton constituency to be issued in Parliament.
The by-election has to take place between 21 and 27 working days from the issuing of the writ, so the poll is likely to fall on Thursday 26 February.
Sir Keir Starmer has opted for the fastest possible by-election timetable in the seat, amid anxiety in the Labour Party about the bitter fallout from a potential defeat.
The Greater Manchester constituency has been represented continuously by Labour for more than 90 years but sources from different wings of the party fear that the by-election could be won by either Reform UK or the Greens.
The rapid timetable is designed to constrict the amount of time the two parties have to build a campaigning infrastructure in the constituency.
While the decision by the prime minister and other officers from Labour’s ruling national executive to block Andy Burnham, the mayor of Greater Manchester, from becoming the candidate for the seat has been criticised by some MPs, the backlash has not been as great as some allies of Sir Keir feared.
However, several MPs – including MPs who supported the decision to exclude Burnham – said they now believed that if Labour lost the by-election it would trigger a destabilising burst of leadership speculation surrounding the prime minister because he is so closely associated with the decision to bar Burnham.
While a by-election defeat in a formerly safe seat would not be unheard of for a governing party, it would raise the political stakes even further for Sir Keir ahead of the May elections, where the Scottish and Welsh parliaments as well as some councils in England are being contested.
There is a widespread expectation among Labour MPs that at least some of their number would respond to a bad set of results by trying to force a leadership contest.
In the 2024 general election, Gwynne won the seat with just over 50% of the vote share, with Reform UK’s Lee Moffitt second and the Green Party third.
George Galloway’s Workers Party of Britain came fourth, with the party’s candidate Amir Burney getting 10% of the vote.
No party has announced the names of their candidates yet, but selection processes have been confirmed as “in motion” by the Greens, who said local members should have finished choosing a candidate by early next week.
A Liberal Democrat spokesperson said: “When that information is ready to share, we will certainly update you.”
Reform and the Conservatives have been contacted for comment, but Nigel Farage told reporters on Monday that the party’s candidate would be announced on Tuesday.
