Gavin Williamson faces an independent investigation after Conservative MP Wendy Morton referred her allegation of abusive messages to a parliamentary watchdog.
The former chief whip has taken her claim to the Independent Complaints and Grievance Scheme (ICGS), The Independent understands.
Mr Williamson sent WhatsApp messages to Ms Morton in which he claimed she had tried to “f*** us all over” over the lack of an invitation to the Queen’s funeral.
Ms Morton is reportedly taking the matter up with the ICGS because she fears “whitewash” by the Conservative party officials, who launched inquiries when the initial complaint was made.
Rishi Sunak is under increasing pressure over his decision to bring Mr Williamson back into government, with a senior civil servant at the Ministry of Defence (MoD) telling The Guardian he told them to “slit your throat” and “jump out of the window”.
Sir Gavin, sacked as defence secretary in 2019, issued a statement denying the broad allegations in latest report – but did not specifically deny using the language alleged.
“I strongly reject this allegation and have enjoyed good working relationships with the many brilliant officials I have worked with across government,” he said. “No specific allegations have ever been brought to my attention.”
The newspaper said the MoD official, who later left government, raised the alleged incidents with the department’s head of HR. But it was understood the Cabinet Office’s propriety and ethics team has not received an official complaint about Sir Gavin’s conduct.
Cabinet minister Mel Stride has said it would be “utterly, utterly unacceptable” if the under-fire minister did tell a senior civil servant to “slit your throat”.
Sir Gavin apologised for sending abusive messages to a colleague at Tuesday morning’s cabinet meeting, fellow cabinet minister Grant Shapps has said.
Asked if Mr Williamson is a bully, business secretary told reporters: “Not in my experience. Clearly he shouldn’t have sent those (messages), he’s recognised that and he’s apologised about it.”
Speaking about the alleged “slit your throat” comments, he added: “I don’t think there was a formal complaint, so let’s wait and see what’s said about that.”
Asked about the pet tarantula Mr Williamson kept in his office while he was chief whip, Mr Stride said: “The reality with Cronus is he was much touted but he never actually was released to bite anybody.”
Labour’s shadow home secretary Yvette Cooper said there was a “lack of proper standards” in the Sunak government shown by the appointments of Sir Gavin and home secretary Suella Braverman.
One the “slit your throat” claim, Ms Cooper told BBC Radio 4’s Today programme: “He doesn’t deny using the language. The language is horrible and you can’t imagine people being treated like that at work.”
On Ms Morton’s referral of her claim to the ICGS, Labour chairwoman Anneliese Dodds said: “The lack of faith in the Conservative Party complaints process shows how rotten the culture at the heart of this party goes – and the buck stops with Rishi Sunak.”
Former Tory chair Jake Berry said he informed Mr Sunak on the day he took the reins as Tory leader that Ms Morton had lodged a formal complaint over the messages.
Mr Sunak – who has insisted he was unaware of the details of the WhatsApp exchange – said on Tuesday that he had been “very clear that language is not right” but urged for patience in the internal Tory investigation before “passing judgment”.
Conservative former cabinet minister Baroness Morgan said she had “run-ins” with Mr Williamson when he was Theresa May’s chief whip, adding: “None of this surprises me, sadly.”
She told TalkTV on Monday: “Unfortunately Gavin has a reputation, it’s not a very nice one, and I really don’t know why Rishi Sunak felt he had to have him back in government.”