Rachel Reeves should resign if Wednesday’s Budget results in more people paying more tax, according to the man whose job it is to hold the Chancellor to account. Sir Mel Stride is known in Parliament for his personal warmth and bonhomie but he has a stern message for Ms Reeves as she finalises her Budget.

Keeping the point at which people start paying tax frozen for longer would, the Shadow Chancellor argues, break a manifesto promise. He said: “I think if she puts taxes up in this Budget, having said that she wouldn’t and given the mess she’s created, she should step down.”

The resignation of a Chancellor would send shockwaves through the economy and could put Sir Keir Starmer’s position at even greater risk.

“Clearly, if she goes then his position becomes much less tenable as well,” he said.

Sir Mel is not one of politics’ natural Rottweilers but his anxiety about the state of Britain in 2025 is clear.

“It’s not good for the country that we’re even discussing this scenario,” he said.

The point at which people begin paying tax was frozen by the Conservatives after the pandemic but this is due to end in 2028. There is alarm that more pensioners will have to pay income tax if it is not uprated. However, there is strong speculation the freeze could continue for two more years in a bid to boost Treasury coffers by approximately £8billion.

Labour’s manifesto stated it would “not increase taxes on working people” and in November last year Ms Reeves told the CBI she would not be “coming back with more borrowing or more taxes”. But with the country thought to be facing a “black hole” in the public finances of tens of billions of pounds, Budget Day is expected to be an expensive exercise in assuring the markets that Britain is not hurtling into a crisis.

Sir Mel anticipates the Budget will bring pain to the people Labour pledged to protect.

“It’s going to hit hard-working people,” he said. “That’s what’s going to happen.”

He argues “there is an alternative” and that the Government could have chosen to control spending. But he predicts the extra revenue will go towards funding welfare payments.

“It’s a straight transfer from people working to people on benefits,” he said.

He claims the Government cannot control left-wing backbenchers who sabotaged attempts to reform welfare earlier this year and “it’s working people who are picking up the tab”. It takes a “particular level of incompetence” for a landslide-winning PM not to be able to get legislation through, he argues, describing Sir Keir Starmer’s position as “extremely precarious”.

If he found himself in a lift with Ms Reeves, he said he would urge her to “grip spending” and “grip welfare” – and offer her Conservative support to get measures past Labour’s backbenchers.

“I think she’d probably get out of the lift at that point, or push the emergency button,” he admitted.

He criss-crosses the country as Shadow Chancellor and is concerned at the signs of belt-tightening and the erosion of business confidence. The day before he spoke to the Sunday Express he was in Billericay in Essex, where he was told in a cafe that people who used to drop in for coffee and cake are now forgoing the cake.

Employers are worried about the hike in their National Insurance contributions and also about the turbo-charged package of workers’ rights Angela Rayner spearheaded before she was forced to resign. A key concern is that young people will find it even harder to get a first job.

He sees trade union pressure as being behind the Government’s decision to stick with Ms Rayner’s reforms, despite flat-lining growth and rising unemployment.

“The most logical thing the Government can do – it won’t cost any money – is just row back on these additional burdens,” he said.

Ms Reeves, he added, “doesn’t have to sign a cheque. She simply has to change the policy.

“The fact they’re not saying they’re going to do that tells you a lot about where the power lies in the modern Labour party, I’m afraid, and it’s not on the side of business.”

Sir Mel, 64, ran his own marketing, publishing and events business before entering Westminster and he has a passion for entrepreneurship. Freeing people from business rates and red tape could unlock a revival of Britain’s beleaguered high streets, he argues.

“If you do those things you can bring them to life very quickly because there are very entrepreneurial people out there and it’s remarkable how resilient they are, actually,” he said. “They just need a break.”

In his eyes, the men and women who keep the wheels of commerce turning also keep Britain alive, able to fund its armed forces and care for the vulnerable.

“The one way to a more prosperous and secure country is though business,” he said, adding: “It’s those armies of people out there getting up and doing what they do who are the difference between us being able to defend ourselves against Vladimir Putin or not having the wherewithal to do it.”

Lifting burdens off British industry is a core goal for Sir Mel, and he wants lowering energy costs to be a national priority.

On a recent visit to the United States he watched robots working on Tesla vehicles. He thought of how much it would cost to power a similar operation in the UK.

He said: “We’ve got four of five times the energy costs of California. They are paying a quarter of the energy a car production unit would over here, so how can you compete?”

Labour’s manifesto contained a pledge not to issue new licences to explore new oil and gas fields. Sir Mel finds the Government’s position “bonkers”.

Pointing to imports of liquified natural gas from the US and Qatar, he said that “has a carbon footprint that’s four times the gas that’s coming out of the North Sea”.

On Tuesday, YouGov reported the Greens were tied with the Tories on 17% when it came to the public’s voting intentions. The Central Devon MP urges voters not to embrace Zack Polanski’s party.

“Look very closely at their economic policies because if you’re worried about Labour then be very, very worried about the Greens,” he said. “I think they would be absolutely ruinous.

“That’s what I would say to people flirting with that.”

Reform UK were 10 points ahead of the Tories in the poll. He describes that party as a “one-man band” and encourages voters to ask: “Do their plans add up?”

Turning around the fortunes of the Conservative party would be an epic challenge for any of the entrepreneurs and innovators he so admires and there are years to run before the next election.

He speaks warmly of party leader Kemi Badenoch, saying: “I think she has got stronger and stronger.”

And he does not doubt the urgency of the task before them.

Describing the nightmare scenario of a “reckoning” with the markets on Labour’s watch, he said: “Let’s hope that doesn’t happen but I think most economic commentators would think that is on the table as a possibility, which is a deeply depressing thing to be thinking about.”

For this father of three, reviving the Conservative party is about more than party politics. He gives the sense of a man who is on a rescue mission.

He said: “We have got to keep going because I think we have the only answer to the challenge that our country faces.”