The head of the civil service is facing pressure from ministers and No 10 insiders to bring forward his departure date, amid anger over a series of damaging leaks and briefings. In a sign of how low relations between ministers and Simon Case have sunk, the cabinet secretary has been privately accused of failing to get a handle on leaks about donations funding clothes for Keir Starmer and his wife, and rows involving his chief of staff Sue Gray. It is understood that cabinet ministers and senior No 10 officials have become so frustrated with the leaks, including on internal appointments and donations, that they have raised informal complaints in meetings. “You can feel the anger in the cabinet, the spads and the civil service rising,” one cabinet source said. Case is expected to leave his role in January but there has been no formal announcement. A Cabinet Office spokesperson denied he was the source of any leaks or negative briefing. The spokesperson said: “We take the unauthorised disclosure of information very seriously and take appropriate action where necessary.” Anger at the briefings was raised again among senior staff in Downing Street over the weekend when yet more damaging details of failures to declare donations to the prime minister’s wife from the Labour peer Waheed Alli were revealed in the Sunday Times. Another Labour peer close to the prime minister expressed frustration that Starmer could not prevent the alleged briefing war between his permanent secretary and staff. Officials have internally described the relationship as toxic and obstructive. Sources said there was anger at a number of leaks that were personally damaging to the prime minister. In August, it was revealed Alli had been given a temporary No 10 pass and organised a reception for donors in Downing Street. There have been a number of stories about the alleged difficult relations between Starmer’s closest aides – the chief of staff, Sue Gray, and the director of political strategy, Morgan McSweeney. And there have also been embarrassing briefings about Gray allegedly preventing access to Starmer, including on security matters, which has been denied, as well as her alleged push to fund a rebuild of Casement Park in west Belfast. On Monday, the Conservatives wrote to the parliamentary standards commissioner to call for an investigation into Starmer’s failure to declare donations from Alli. No 10 said it had self-reported when the error had become clear. On Monday evening, the parliamentary commissioner said there would be no investigation into Starmer over the late donations. Speaking to reporters on a visit to Italy, Starmer rejected suggestions that questions around whether he failed to declare donations of clothes for his wife, Victoria, could have been avoided if the government had a corruption adviser. The prime minister said: “There’s a massive difference between declarations and corruption. Declarations is about declaring properly so you and everybody else can see properly made declarations.” Gray worked under Case while a civil servant in Whitehall, including while she authored the investigation into Boris Johnson’s Partygate misdemeanours and the pair are said to have clashed. When asked by reporters late last week if Gray had “become the story”, Starmer said: “I’m not going to talk behind her back and I’m not going to talk about individual members of staff, whether it’s Sue Gray or any other member of staff. All I can say about the stories is most of them are wildly wrong.” Case is expected to say he intends to leave in the new year owing to health reasons, but there has been no formal announcement. Once the departure date is fixed, a formal process can commence including the involvement of the Civil Service Commission. The Guardian previously reported that senior figures in No 10 are very keen to kickstart the process. The Cabinet Office has denied Case is behind any leaking, including on the alleged tensions between Gray and McSweeney. A spokesperson called it “categorically untrue”. Case is understood to have made it clear to the prime minister that he intends to leave the role, without giving the specific date, and sources close to Case stressed the conversation would be between him and Starmer alone. He took a medical leave of absence late last year, returning in January. Gray, Starmer’s powerful chief of staff who previously held several high-profile roles in Whitehall, is said to favour replacing Case with Oliver Robbins, the former Brexit negotiator, or Tamara Finkelstein, the permanent secretary at the Department for Environment, Food and Rural Affairs. But there are also strong views from others in No 10 that the next permanent secretary should be a personal appointment by Starmer and able to demonstrate they are a part of the government’s change agenda, rather than a civil service lifer. Sharon White, the chair of John Lewis who was the former chief executive of Ofcom, is also believed to be in the frame. The Guardian revealed last month that Starmer had cancelled the appointment of one of Britain’s top generals as the national security adviser, another job for which Robbins could be considered. The prime minister overturned the decision made in April by his predecessor, Rishi Sunak, to appoint Gwyn Jenkins, then the vice-chief of the armed forces.