It is one week today until the crunch Gorton and Denton by-election, which poses a fresh potential blow to Sir Keir Starmer. The Prime Minister survived the biggest crisis of his leadership so far earlier this month over the Lord Mandelson scandal.

But Sir Keir remains in jeopardy despite coming out fighting, and the contest in what used to be a safe Labour seat next Thursday could further damage him. The by-election is seen as a three-horse race between Labour, Reform UK and the Greens. Labour won the Manchester constituency with a majority of more than 13,000 at the 2024 General Election.

In the 19 months since, both the Prime Minister and the party’s popularity have nosedived following a series of scandals and more than a dozen U-turns, including the deeply damaging pensioner winter fuel payments row and the latest climbdown this week on postponed local elections.

Sir Keir had also sparked anger from MPs within his own party, with one Labour backbencher warning earlier this month: “I don’t know if it will be this week or next week or later, but he has to go.”

Meanwhile, Nigel Farage‘s insurgent party has consistently been leading national opinion polls, and the Greens have also seen a rise in support under new leader Zack Polanski.

Labour was immediately engulfed in a row over the by-election after Greater Manchester Mayor Andy Burnham, a popular figure in the region, was blocked from standing amid fears that a return to Westminster would see him launch a leadership challenge against Sir Keir.

The party instead selected Manchester councillor Angeliki Stogia as its candidate, which was sparked by the resignation of the former Labour MP who cited health reasons.

If Labour loses the seat, the blame could be pinned on the refusal to allow Mr Burnham to run, which the party’s ruling National Executive Committee argued was to avoid a new mayoral election in Greater Manchester.

Reform leader Mr Farage declared that his party’s prospects in the seat, which is way down its target list at number 520, were boosted following the blocking of Sir Keir’s potential leadership rival.

A Reform source has insisted it will be a “very close-fought battle” but that the party is in with a chance, and would be an “extraordinary achievement” if it did win.

Last year, Mr Farage’s party was victorious in a dramatic by-election in the traditional Labour seat of Runcorn and Helsby by a wafer-thin six votes.

If Reform wins Gorton and Denton, it will show that Mr Farage is doing well in what were Labour’s northern heartlands.

In what has been an increasingly bitter by-election, Labour’s deputy leader Lucy Powell has insisted that voting Labour is the only way to keep Reform out.

But the Greens have claimed that the race is between them and Reform as they look to take votes on the Left.

Mr Farage will be hoping that a split in the Left-wing vote will pave the way for Reform candidate Matt Goodwin, an ex-academic and GB News presenter, to go through the middle.

A Labour loss would be yet another blow to the embattled Prime Minister, who the Tories have accused of being “in office but not in power”.

It would further weaken his position, with growing disquiet within the party likely to intensify.

And it would fuel the ongoing speculation about how much longer he will remain in 10 Downing Street, less than two years on from his landslide majority.

However, he is unlikely to be forced out before the May elections, where Labour is set to suffer humiliating defeats.

The party is expected to be ousted from power in Wales for the first time in history, while in Scotland, Anas Sarwar – who broke ranks and called for Sir Keir to go over the Mandelson scandal – is struggling against the unpopularity of the UK Labour Government.

And it is also a bleak picture when it comes to the English council ballots.

It means that even if Labour does win the high-stakes by-election in what would be a sigh of relief for under-pressure Sir Keir, he will remain in danger in the coming months.