In this hypothetical scenario, Reform UK would win 60% of the seats with 31% of the vote, while Labour would slump to just 85 seats, a loss of 326 seats from their July 2024 landslide.

Luke Tryl, More in Common UK director, said: “Reform continues to hold poll position in our MRP. Based on polling since the budget, it suggests that in an election tomorrow, Reform could hope to secure a substantial three-figure majority. Meanwhile, the Polanski surge sees the Greens continue to make gains, with disillusioned progressives putting them within shouting distance of many more gains from Labour.

“On the other hand, Labour would slump to a modern low, losing over half of the total number of seats in Parliament and being reduced to just 85 MPs. While the Tories would lose a further 50 from their 2024 nadir, this projection actually represents an uptick in the Tories’ fortunes and signs that the Badenoch bounce may at least be stabilising their position in places like the ‘Blue Wall’ – even as they lose seats to Reform in their Brexit-voting former heartlands.”

While this projection represents a loss of over 50 seats for the Conservatives, for the first time in a year, the number of seats More in Common’s MRP model projects the Conservatives to win has increased from the previous model.

The Greens are projected to more than double their parliamentary presence from 4 to 9 seats, but half of the current Liberal Democrat MPs are projected to lose their seats.

Mr Tryl said: “But there is one major caveat: tactical voting. For the first time, we have explored how tactical voting could reshape the model projections. It suggests the Liberal Democrats could be big winners here – and if that if tactical voting is anywhere close to the scale we saw in Caerphilly, that parties of the left could deny Reform a majority and form a rainbow coalition of their own.

“The threat of tactical voting, combined with the narrow margin of many of Reform’s projected victories, suggests their momentum may have at least temporarily stalled. That, combined with the fact we are still years from an election, means that despite their success in 2025, the path to the next General Election is still far from known.”

The Labour Party begins the new year in its worst position ever in the polls at 18.5%, Electoral Calculus said.

But Sir Keir Starmer insisted he would still be Prime Minister next year.

Speaking to the BBC’s Laura Kuenssberg in Downing Street, he said: “I will be sitting in this seat by 2027.”

Asked whether he wanted to acknowledge the “hole” he was in amid backbench discontent and poor poll ratings for Labour, he said: “I’m not surprised that people are frustrated. I completely get that.

“The truth is, since the crash in ’08, most people haven’t seen their living standards improve, they haven’t seen their public services move in the right direction, they’ve seen them move in the wrong direction, and they’ve lost trust in politics.”

He said he was given a “five-year mandate” to “turn this country around”.

“And I said we’d do it in a serious way with long-term measures that would actually benefit the country; not slogans, not easy answers, not all the things that failed so miserably over the last 14 years in the last Government – do it differently – and that’s what we’re doing.”