Deputy Prime Minister Dominic Raab is facing a third formal bullying complaint - this time relating to his role as Brexit secretary.
It means he is now being formally investigated over three complaints in three different government departments - piling pressure on Rishi Sunak who has resisted calls to sack him.
Mr Raab was already facing formal complaints relating to previous roles as the justice secretary and foreign secretary.
It follows a string of bullying allegations that have emerged since the senior Tory was drafted back into Mr Sunak's cabinet as deputy PM and Secretary of State for Justice - roles he held under Boris Johnson before being sacked by Liz Truss.
Mr Raab denies all allegations of bullying made against him, but last week asked the PM to launch an inquiry into his own conduct.
The scope of this investigation has now been expanded to cover a third complaint relating to Mr Raab's time as Brexit secretary from July to November 2018, when Theresa May was prime minister, Downing Street said on Friday.
"I can confirm that the prime minister has now asked the investigator to add a further formal complaint relating to conduct at the Department for Exiting the European Union and to establish the facts in line with the existing terms of reference," the PM's spokeswoman said.
The complaint was received on 23 November, she added, confirming that Mr Sunak retains confidence in Mr Raab.
Responding to the latest allegations, Liberal Democrat Chief Whip Wendy Chamberlain MP said: "Another day, another bullying complaint against Dominic Raab. It seems that at almost every department he's served in, Raab has treated his staff with contempt.
"This flood of allegations about Dominic Raab's bullying behaviour cannot be swept under the carpet. Rishi Sunak must confirm he will sack Raab if these complaints are upheld."
Raab 'behaved professionally at all times'
Last night, Mr Raab insisted he has "behaved professionally at all times" as he faced fresh allegations of bullying and intimidating behaviour.
Yesterday a number of the deputy PM's former private secretaries told the BBC they were preparing to submit formal complaints about his behaviour.
Newsnight was also told that Mr Raab used his personal email account for government business at two separate departments - once as recently as 2021.
But Mr Raab said: "I have always adhered to the ministerial code, including the use of my iPhone."
The government has appointed senior lawyer Adam Tolley KC to "establish the specific facts" about the formal complaints.
The lawyer will report to the prime minister, who will make the final judgement on whether his conduct breached the ministerial code.
Downing Street has rejected suggestions the investigation would be a whitewash, despite Mr Sunak's ability to reject its findings.
"It's a long-standing convention that the prime minister of the day is the arbiter of the (ministerial) code and the final decision-maker on these sorts of issues," the prime minister's official spokesman said yesterday.
"The investigator looking into this is highly experienced and has a suitable background, and is being given access to whatever they need to conduct a thorough and swift investigation."
Mr Raab is a close ally of Mr Sunak.
Deputy Labour leader Angela Rayner has called for the scope of the investigation to be expanded to include expressions of concern and informal complaints.
"There must be no hint of a whitewash when it comes to the slew of serious allegations the deputy prime minister now faces," she said.