Frustrations are growing in the Treasury at No 10’s handling of significant political decisions after a series of botched announcements, with sources calling for a shake-up of the Downing Street operation. After a tumultuous three weeks marred by repeated backbench revolts, Rishi Sunak’s department is understood to be concerned about the prime minister’s tendency to over-promise and the fumbled timing of decisions. The announcement of the integrated rail plan, originally scheduled for earlier in the autumn but delayed until last week, was among poorly executed announcements, Treasury sources believe. After a series of leaks, the final plan was greeted with fury, including by many Tory MPs, after it fell short of what had been promised by Boris Johnson. “In the end what happened was that we blew a £96bn announcement that really should have been a lot more positive,” a Treasury source told the Guardian. A No 10 source said: “I’m not really sure how moving a date on the calendar would have made a substantive difference.” With some MPs blaming Johnson’s inveterate boosterism for the dashed expectations that led to a string of northern newspaper front pages condemning the plans, the source added that there needed to be “more care taken” before pledges are made. Details of the social care cap were also delayed until last week, months after the broader package was announced, focusing anger on the disproportionate impact on lower-income households. Scores of Conservative backbenchers voted against the plans or stayed away on Monday, reducing Johnson’s majority to just 26. Some privately voiced growing concerns about Johnson’s competence before the vote and after a rambling speech to business leaders. On Tuesday Johnson’s official spokesman was forced to insist “the prime minister is well” after the speech to the CBI in which he lost his place and digressed to praise Peppa Pig World. But many Tory MPs blame Sunak, who is understood to have had dinner with the prime minister on Sunday, for forcing the government to pare back its investment plans to save money. On Tuesday some Conservative MPs urged Johnson to bring in a political heavy-hitter to help rectify the situation and bring an end to what are regarded as unforced errors by Downing Street. “He’s absolutely got to do something,” said a former minister. “All of us have weaknesses; it’s incumbent on us to put the right people in place to correct for those weaknesses.” One MP placing the blame on Johnson’s aides said part of the problem was the lack of seniority in the No 10 team. “There’s no one in there who is his age or older than him,” he said. Another said there would need to be “more big beasts than the cast of a Ben-Hur movie” to rein Johnson in. A suggestion being mooted on Whitehall – including in the Treasury – is that Ben Gascoigne, Johnson’s former political secretary who was recently brought back in as deputy chief of staff, could help take more of a strategic oversight role. Rumours have also resurfaced that Johnson’s chief of staff, Dan Rosenfield, could depart – though he was closely involved in many recent decisions, including the prime minister’s ruthless September reshuffle. Rosenfield regards his role as building a machine to allow Johnson to govern effectively, though some Johnson allies believe he lacks political nous. A senior Tory who knows Johnson well said: “It’s easy to blame the team – the fact is [Johnson] just isn’t up to it. His whole personality would have to change. He would need to trust someone and let them have real power to fix the operation – and him. He doesn’t trust anyone.” Another Tory observer said Johnson’s judgment was looking “irredeemably flawed” and this had led to MPs losing confidence in where the prime minister was choosing to spend political capital. “If we hadn’t just had a reshuffle, the case for changes would already be growing quite strong,” they noted. Despite tensions over how policy announcements are being presented, Treasury sources insisted no one at No 11 had been responsible for an incendiary briefing to the BBC on Monday, attributed to a “senior Downing Street source”, that pointed to “a lot of concern inside the building about the PM”. Johnson’s spokesman rejected the idea that ministers felt unable to tell the prime minister if they felt he was on the wrong course. “The prime minister has an entire cabinet to draw on, who provide advice, as you would expect, and the cabinet is used for that purpose,” he said. “Of course the prime minister wants people to be able to speak freely and give their views. That’s what cabinet meetings are for. That’s part of the function of government, to have open conversations.” Johnson’s recent woes began when he backed an ill-fated attempt to prevent Owen Paterson from being punished for repeatedly lobbying the government on behalf of two companies that were paying him more than £100,000 a year. In a rare apology, the prime minister admitted last week that he had “crashed the car into a ditch” by initially supporting Paterson and then changing his mind. He has since backed calls for MPs to be banned from carrying out paid political consultancy. Chris Bryant, chair of the cross-party standards committee, has said it will publish a review of the code of conduct for MPs next Monday. The committee was already examining whether the rules on MPs’ second jobs should be tightened, before the Paterson scandal brought a fresh spotlight to the issue. Asked about Johnson’s CBI speech, his spokesman said on Tuesday: “The prime minister briefly lost his place in the speech. He’s given hundreds of speeches. I don’t think it’s unusual for people, on rare occasions, to lose their place in space.” Asked about a potential shake-up in the No 10 team, a source insisted: “Downing Street is focused on delivering for the public and the team is united around that goal.”