Sir Keir Starmer has suffered the biggest fall in popularity for a new Prime Minister, a humiliating poll has revealed.

The PM’s approval rating has plummeted from a high of plus 11 in July – after Labour won a landslide 174-seat majority – to minus 38, a survey by More in Common has found.

It comes amid widespread fury over the upcoming Budget, the axing of the winter fuel payments, freebies and the Channel migrant crisis.

The Chancellor is planning to announce a cut to the earnings threshold at which employers pay national insurance and an increase in the rate of contributions.

Capital gains tax, inheritance tax and fuel duty are also expected to be in her sights.

Meanwhile, the £2 cap on bus fares introduced by the Conservatives will be lifted to save cash.

Sir Keir’s falling popularity takes him below his predecessor, Rishi Sunak’s rating of -37 when he lost the election to.

Sir Tony Blair, who led Labour to a landslide win in 1997, had a popularity of plus 46 three months later.

It took three years before he dropped into minus figures.

Boris Johnson, who started off at -20 despite winning the 2019 election, had turned his rating around to plus three by January and then plus 14 by the following March.

Luke Tryl, the executive director of More in Common, said the collapse in Sir Keir’s approval rating was “unprecedented” compared with other prime ministers in the modern era.

He also suggested the electorate had become more volatile over the past couple of decades, and added: “Although they had a landslide, in terms of popularity they didn’t have the slack to spare that other new governments had.”

Sir Keir has said Labour would not continue the “fiction” that you can have lower taxes and public services that run properly, in a speech ahead of the Budget.

Asked if his priorities were out of step with the public mood after a poll suggested most voters would prefer lower taxes rather than investment in public services, the Prime Minister said: “No. I think for too long, we pretended that you could lower tax and spend more on your public services, but you can’t. And it’s about time we faced up to that.”

He added: “Almost everybody knows the NHS is broken. We’re going to fix it, put it back on his feet, and make it something we can be proud of again.

“That’s the path we’re choosing, and that’s what we’ll deliver for working people.

“But what we’re not going to do is continue the fiction that got us here in the first place, the pretence that you can always have lower taxes and that your public services will run properly.

“Because the last 14 years have shown this is completely and utterly untrue, and people voted for change.”

And the Prime Minister rejected claims that changing the way debt is measured will affect interest rates and make mortgages or debt more expensive.

Asked about planned changes to the debt rule to borrow more for investment into capital expenditure, Sir Keir said: “I’m not going to pre-empt exactly what the Chancellor will say on Wednesday, but I have been really clear that we have to move to a situation where we invest in the future of this country.

“Where we invest to ensure that we get the better jobs that we need, we have the infrastructure that we need.

“And so part of what we will say on Wednesday is, first, how we’re going to fix the foundations and deal with the problem we’ve inherited, but secondly, how then we rebuild the country.

“And investment is an important part of that story. Precisely how that will take place will be set out in detail on Wednesday. I do not accept the proposition that it will have an impact on interest rates.”