Dominic Raab has vowed to quit Rishi Sunak’s Cabinet if he is found guilty of bullying staff.

The deputy prime minister is facing an ongoing investigation into how he treated a number of government officials.

However, he refused to step down ahead of the investigation into his behaviour, saying “innocent until proven guilty”.

Staff from multiple departments he has led have made complaints about his behaviour – including at the Brexit department, foreign office and ministry of justice.

He is being investigated by senior lawyer Adam Tolley KC, with dozens of officials thought to be involved in eight formal complaints.

Raab told Sky’s Sophy Ridge On Sunday programme: “I’m not going to start speculating on what the outcome might be. Again, you’re asking me to comment on the subject matter.”

The justice secretary dismissed calls to stand aside while the probe is carried out but added: “Allow me to respond in the right way at the right time, of course. Look, if an allegation of bullying is upheld, I will resign.”

Former Tory chair Jake Berry has called on Raab to step aside from his ministerial roles while he is investigated over the claims.

Rishi Sunak has resisted calls for Raab to be suspended or to step aside while he is investigated, with the prime minister instead waiting for the inquiry to conclude.

The PM has faced questions over what he knew about the allegations before appointing Raab as his deputy and justice secretary, with Downing Street only ruling out Sunak being aware of “formal complaints”.

Raab has previously said he is not a bully and always “behaved professionally” towards staff.

Asked on the BBC’s Sunday with Laura Kuenssberg if he was a bully, Raab replied: “No.”

Dave Penman, general secretary of the FDA union, which represents senior Whitehall officials, previously suggested whistleblowers working at the ministry of justice are going through a continuing ordeal.

“I can’t imagine what it’s like to be one of those complainants working in a department where Dominic Raab is still the secretary of state,” he told GB News.

Allies of Raab have suggested civil servants are trying to push him out. However, Penman hit back at claims that he is the victim of a smear campaign, saying it is “really difficult” to accuse one of “the most powerful people in the country” of bullying.

Lib Dem chief whip Wendy Chamberlain said Sunak must “come clean” about what he knew when.

“Rishi Sunak should finally show some backbone and suspend Raab while this investigation is ongoing,” she said.

“That is what would happen to someone facing such serious allegations in any other workplace.

“The current position is completely unsustainable, how can crime victims expect justice when the minister responsible is busy trying to clear his own name?”