Dominic Raab is facing a much broader bullying investigation than originally anticipated with at least 24 civil servants involved in formal complaints against him, the Guardian understands. Government insiders believe the depth of the inquiry and severity of some of the claims means the deputy prime minister will struggle to survive in post, and throws further doubt on Rishi Sunak’s judgment for having him in such a senior position. The prime minister is already under siege on a separate front over the tax affairs of the Conservative party chair, Nadhim Zahawi, with growing pressure on him from senior Tories and the opposition to take decisive action irrespective of an ongoing inquiry. Downing Street confirmed in December that the justice secretary was facing eight formal complaints over alleged bullying, six of them from his first stint at the Ministry of Justice (MoJ), one from when he was foreign secretary and one from when he ran the Brexit department. However, sources said that all but two of the formal complaints involved multiple accusers with a number of his private office staff from his first stretch at the department believed to have made submissions. The total number of complainants is thought to be at least two dozen, and could be more than 30, sources claim. The Guardian understands that Sunak personally read excerpts from a number of the written statements submitted as part of the initial tranche of complaints before ordering the investigation by Adam Tolley KC into potential breaches of the ministerial code. The deputy prime minister, who has stayed in post while the inquiry is ongoing, has vowed to “thoroughly rebut and refute” the formal complaints. He has said he is confident he “acted professionally” throughout his time in three different cabinet posts. However, the latest claims will come as another blow as he attempts to move on from the scandal. Raab faces potentially damaging allegations over bullying behaviour when dealing with civil servants, including some in senior roles, including that he “belittled and demeaned” them and was “very rude and aggressive” on multiple occasions each day. Officials close to the inquiry are said to have been shocked by some of the claims that have emerged including individuals being physically sick before meetings, regularly in tears and, in more than one case, left feeling suicidal as a result of the alleged behaviour. The inquiry, which began in December, is expected to conclude within weeks after Tolley held lengthy sessions with complainants. He will interview Raab, who will be able to consult lawyers before and after, although interviewees are not permitted to bring along legal representation. Downing Street has denied suggestions Sunak is aiming for the Raab inquiry to be completed at the same time as the ethics investigation into Zahawi – so that both ministers could be sacked on the same day as part of a mini-reshuffle to divert attention – pointing out that the inquiries are on separate timetables. However, Tory MPs are privately concerned that the prime minister’s handling of the two rows could undermine his pledge to instil “integrity, professionalism and accountability at every level” of his government as he tries to move the party on from the Boris Johnson era. The Guardian first revealed in November last year that senior civil servants at the MoJ were offered “respite or a route out” of the department when Raab was reappointed by Sunak, having been sacked from the role by Liz Truss, amid concerns that some were still traumatised by his behaviour during a previous stint there. Antonia Romeo, the MoJ permanent secretary, spoke to Raab when he came back to the department to warn him that he must treat staff professionally and with respect amid unhappiness about his return, according to sources. The Observer revealed that concerns over Raab’s behaviour towards officials were raised inside Whitehall during his time as Brexit secretary in 2018, with a document outlining a “serious expression of concern” dispatched to the Cabinet Office by a prominent official in the former department. Days later, the Guardian reported that Raab was also warned about his behaviour towards officials during his time as foreign secretary by the department’s top civil servant, who then informally reported his concerns to the Cabinet Office’s propriety and ethics team. The deputy prime minister claimed in an interview with ITV that “no one has ever raised a complaint or grievance with me”. But Simon McDonald, the permanent secretary at the Foreign Office at the time, later refused to deny he had spoken to Raab, agreeing that the characterisation of him as “a bully” was a plausible one. An MoJ spokesperson said: “There is zero tolerance for bullying across the civil service. The deputy prime minister leads a professional department, driving forward major reforms, where civil servants are valued and the level of ambition is high. “There is an independent investigation under way and it would be inappropriate to comment further on issues relating to it until it is completed.” A Cabinet Office spokesperson added: “The investigation by Adam Tolley KC is ongoing so it would be inappropriate to comment further whilst that process takes place.”