Amid the plummeting markets and polls this week, a senior government figure approached No 10 and urged it to change course. They were summarily rebuffed.

“It’s like talking to crack addicts,” they said. “You’re saying you guys need to stop, you need to temper your approach, we’ve got to communicate better. But they’re doubling down.

They’re hooked on the economics.”

Liz Truss, the prime minister, is adamant that she is taking the right approach. She views the market’s response, a collapse in the value of sterling and government bonds, as an overreaction based on a failure to understand the full extent of her plans for government.

Her approach is said to be even more hardline than that of Kwasi Kwarteng, her chancellor, who on Monday had to persuade her to issue a statement in response to the tanking pound in an attempt to steady the markets.

Truss knew that the £45 billion package of tax cuts was likely to provoke some turbulence in the markets. She had not anticipated, however, the full extent of that turbulence or just how unpopular the budget would prove to be.

She was frustrated by the Treasury’s failure to anticipate and manage events, although sources emphasised that this was directed at the institution rather than at her chancellor. “There’s a feeling there’s been bad comms and stakeholder management,” a government source said.

Truss’s senior aides were said to have vented their anger at being blindsided by the market chaos. “ No 10 is a complete mess,” said one senior Conservative who has spoken to officials in Downing Street. “People are going round saying, ‘Why weren’t we warned?’. But the problem is that she [Truss] hollowed the whole structure of the building and got rid of anyone who was experienced.”

Despite what one insider acknowledged was a “brutal” week, Truss and her team are said to be “calm” and determined to press ahead. “The thing is they are all true believers, so there is no, ‘Oh shit, the headlines are terrible, we have to change course,’” said one aide who has been working in No 10 this week.

“There will be no more drawn-out U-turns. They’re not panicking because they really believe it will work.”

Kwarteng has “complete confidence” that the government is taking the right approach, a message he will be conveying in his speech at the Conservative Party conference on Monday. “We are 12 years into a Conservative government and somehow we have sleepwalked into having the tax burden at a 70-yearhigh,” he told aides at the weekend.

But if Truss and Kwarteng are broadly unconcerned, the same cannot be said for the general public.

This week has been punctuated by two extraordinary YouGov polls for The Times, the first of which put Labour 17 points ahead and the second 33 points.

Truss has in effect been at the helm for just over a week, given the period of national mourning, but many of her MPs are facing what they believe is an existential crisis. If YouGov’s polling was translated to the electoral map — a hypothetical exercise but one being looked at intently by Tory MPs — the Conservatives would be left with just two seats, under some calculations.

They are particularly alarmed by soaring mortgage rates, which will directly hit homeowners, the Conservative Party’s traditional base.

“The fatal thing they did was directly connect Conservative government action with rising mortgage rates,” a government source said. “That is the cardinal sin they have committed.

That is the reason you can’t turn it back.” The concern is not limited to former supporters of Rishi Sunak but extends even to those who backed Truss for the leadership and serve in her government.

“This has been completely selfinflicted,” said one senior Tory who supports Truss.

“There was no reason at all why Kwasi needed to announce the tax cuts before laying out the supply-side reforms that were going to pay for them. And he then doubled down, promising further tax cuts which just completely spooked the market and led us into a spiral. If you have a problem the last thing you do is double down. We’ve ended up with a perfect storm of problems.”

A cabinet minister added: “This wasn’t Black Wednesday or a crisis anywhere near that scale. But the problem we’ve got is that it’s turned into a political crisis. Our MPs are running around like the sky has fallen in. The optimist in me would say that she’s only been in office five minutes and the public will give her the benefit of the doubt. The fear is that the public has made up their minds and switched off to her.”

Those who were never convinced by Truss in the first place scent blood.

As extraordinary as it sounds MPs are talking openly of ousting a prime minister who has been in Downing Street less than a month.

“She’s done,” said one former Sunak-backing MP. “It took seven months to get rid of Boris, from late December to July. It’ll take Liz seven weeks.”

A senior Tory MP who remained neutral during the Tory leadership campaign said that Truss would be “gone by Christmas” if she did not turn things round by then.

Another MP angry at the “duffers” in ministerial jobs was in no doubt: “We should bring her down. You force Brady [Sir Graham Brady, the chairman of the 1922 Committee] into it, call no confidence and don’t let the contest go to the membership. She’s pretty much got only John Redwood and Daniel Kawczynski defending her in the WhatsApp groups. It’s hardly a winning position. Thing is, what’s to lose? How could it be worse?”

Even Redwood has concerns. On a Tory WhatsApp group this week he criticised the Bank of England for its £65 billion emergency intervention.

“Bank wrong to do more QE as that started inflation in the first place,” he said. Over the coming weeks Truss has made clear she intends to pursue a tough package of government spending cuts alongside potentially unpopular “supplyside” reforms such as abolishing the 48-hour working week, liberalising planning laws and reducing environmental protection. Downing Street is said to be “infuriating” government departments by deluging them with demands to model different types of policy — and then changing their mind and asking for something different.

“Civil servants think this supplyside stuff is laughable,” said a Whitehall source. “They’re lining up to scrap the working time directive altogether, which officials think is beyond naive. The truth is while it is sensible to do things like childcare ratios and banking regulation it is not going to move the dial on growth in the short term. And even if she’s right you’re not going to get business investment because no one believes we’re going to be in power after 2024 and Labour will reverse everything.”

Of particular concern is a mooted plan by the Treasury not to increase benefits this April in line with inflation — but instead by average earnings — to save money.

The Treasury is already eyeing further cuts from welfare, with sources saying they “see it as a big budget we can probably save from”.

Even allies of Truss think this is political madness, allowing the party to be portrayed by Labour as giving tax cuts to the rich while cutting benefits for the poor. “It would be manna from heaven for Labour,” said one Truss supporter. “It is strategically stupid.”

A cabinet minister added that Truss would never get the measure past her own MPs. “After that budget they’re going to have to back down on benefits. They simply don’t have the numbers to get it through the Commons.” All this provides a bleak backdrop to next week’s party conference — which had been planned as a coronation for Truss.

Even the conference’s slogan, “Getting Britain moving”, now has an ironic overtone, because many delegates will struggle to get there during a national rail strike.

One MP who turned down a job in Truss’s government tried to put perspective on how bad things were.

“My dog had his balls chopped off yesterday so it’s a reminder that things can always get worse,” he said.

Additional reporting: Henry Zeffman, Chris Smyth and Matt Dathan