Dominic Raab is facing fresh calls to be suspended from his post, after the Guardian revealed three senior civil servants who worked with him had been interviewed by the official inquiry into his alleged bullying. Rishi Sunak has rejected calls to suspend Raab, the justice secretary and deputy prime minister, despite the number of allegations against him increasing. Antonia Romeo, the permanent secretary at the Ministry of Justice, and Philip Rycroft, who ran the Brexit department while Raab was in charge there, have both been witnesses in the investigation led by Adam Tolley KC, the Guardian understands. The former Foreign Office permanent secretary Simon McDonald is also understood to have spoken to the inquiry. Labour, the Liberal Democrats and campaigners have noted that any other employee in a different workplace would be suspended while such an investigation was taking place. Dave Penman, the general secretary of the FDA union that represents senior civil servants, told BBC Radio 4’s Today programme: “If that was any other employee, if that was a permanent secretary in the civil service, they would in all likelihood be suspended from their job while that investigation took place.” The shadow justice secretary, Steve Reed, said: “Nobody should be subject to bullying and intimidation at their place of work … so in the interests of safety Rishi Sunak should suspend Dominic Raab … but he’s too weak to do that, just like he was too weak to sack [the home secretary, Suella] Braverman, and [the former Conservative party chair, Nadhim] Zahawi.” Raab, 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. Last week, No 10 said the number of formal allegations against Raab remained at eight but could not rule out each complaint including multiple accusers. It comes after the senior Tory MP Jacob Rees-Mogg warned against being “too snowflakey” over bullying allegations as he defended Raab. Rees-Mogg said it was “completely sensible” for Raab to remain deputy prime minister and justice secretary while under investigation. “I think we’ve got to be slightly careful about the bullying allegations. We mustn’t be too snowflakey about it. People need to be able to say this job has not been done well enough and needs to be done better. “It’s a very difficult line to judge. It’s not a straightforward issue in most cases. It’s how did somebody react, what did somebody say, is it reasonable to demand from senior and well-paid professionals a level of good service? And then you have to judge whether that line has been overstepped.” Rees-Mogg backed the then prime minister, Boris Johnson, over keeping on Patel as home secretary despite her being found to have broken the ministerial code over bullying allegations. The education secretary, Gillian Keegan, also defended her cabinet colleague, claiming Raab should not be pushed to quit his roles until the investigation had concluded.