Rishi Sunak has been urged to “come clean” over whether he knew of informal concerns about Dominic Raab’s behaviour before appointing him, as an investigation into the deputy prime minister continues. Eleven weeks since the inquiry began looking into complaints from about two dozen civil servants across three government departments, pressure is growing on the prime minister to suspend Raab and reveal what he knew and when. Dave Penman, the general secretary of the FDA union, which represents many civil servants, criticised Sunak for “point blank” refusing to say whether informal concerns about Raab’s behaviour were raised – and if so “what did he do with that”. After No 10 only ruled out Sunak having been made aware of any formal complaints, Penman said the prime minister should “come clean”. Given the scale of the allegations against Raab, which he denies, Penman said it would be normal in a workplace for such a person to be suspended until the outcome of an investigation was known. “That suggests there’s a real issue there and a real danger for the health and safety of current staff,” he told Sky News. “Until you can establish their innocence, you have to protect your current workforce.” He said it was ultimately important for Sunak to clear up what he knew and when, given he would have to decide what fate Raab should face if the independent investigation led by Adam Tolley KC upheld the bullying complaints. Lisa Nandy, the shadow communities secretary, also criticised Sunak for not disclosing what he knew before he appointed Raab. “This is a prime minister who doesn’t act until he’s forced to, he’s dragged to do it kicking and screaming. He’s far too weak to control his own party and once again the country is paying the price for this ongoing psychodrama.” Ed Davey, the Liberal Democrats leader, suggested Tolley should look into what warnings may have been made informally about Raab’s conduct in the past. “The question marks are now not just about Dominic Raab but about the prime minister,” he said. “Did he appoint Dominic Raab knowing these serious allegations were there?” The No 10 press secretary was repeatedly asked on Wednesday whether Sunak was aware of any informal concerns about Raab’s behaviour when he appointed him as justice secretary in October 2022. They stuck to the same statement, repeating: “The PM was not aware of any formal complaints at the time of appointing Dominic Raab.” The Observer previously revealed that a “serious expression of concern” was dispatched to the Cabinet Office by one of the departments Raab worked at in 2018, and other newspapers have reported that issues with his behaviour had been discussed internally – including with Downing Street. Raab says he has acted professionally at all times, and on Wednesday said “no” when asked if he would resign over the allegations. The investigation is said to be focusing on whether Raab deliberately targeted staff or was oblivious to the impact his behaviour had on them. Raab’s allies have pushed back and attempted to defend him, with a briefing that two officials have so far given evidence in defence of him. One minister also told the Times: “Dom puts the backs up of civil servants because he actually checks the work. He doesn’t just take what they tell him. “You can’t get anything by him. That is a threat. Most ministers [they] can manipulate and push around. “He’s handling some of the most controversial legislation coming up and this is the best way to remove a secretary of state who is going to double down on the detail.”