Nicola Sturgeon is under pressure to disclose whether she knew of Alex Salmond's "bullying and intimidatory behaviour” while he was First Minister after their former top mandarin confirmed he was aware of it.
Sir Peter Housden, who served as the Scottish Government's permanent secretary in the governments of both SNP leaders, admitted that he knew that Mr Salmond "could display those behaviours" with staff.
Questioned by a specially-convened Holyrood committee about the action he took, he said it would be "appropriate to speak with a senior member of the administration" about his concerns.
But three times he refused to confirm or deny he raised the issue directly with Ms Sturgeon, who was Deputy First Minister in Mr Salmond's government for seven-and-a-half years.
Instead, he told the inquiry he was bound by a civil service code of confidentiality not to disclose whether he spoke to a senior minister he spoke to about the bullying and, if so, who.
Sir Peter said Mr Salmond's tenure as First Minister was "punctuated by these kind of behaviours" but he insisted there were "no suggestions of sexual misconduct."
Murdo Fraser, a Tory committee member, said Ms Sturgeon must now urgently confirm whether "she was spoken to by the most senior civil servant about serious harassment claims within the Scottish Government."
Jackie Baillie, a Labour committee member, said Sir Peter's testimony had provided the inquiry with further evidence that "bullying was endemic in the Scottish Government and the civil service."
She also ratcheted up the pressure on Ms Sturgeon, who will appear before the committee later, by stating it is now "clear that many of those currently at the heart of the Scottish Government were aware of the concerns being raised at the time."
In another major development, Mr Salmond threatened the SNP government with further legal action to stop it releasing evidence about him to the inquiry that "represented a clear breach of court orders and undertakings."
The former First Minister’s solicitor warned his client is ready “to return to court” to stop the Government releasing information about its in-house sexual misconduct probe into Mr Salmond, as it would be “a clear contempt of court”.
David McKie, a partner with Levy and McRae Solicitors, also accused the SNP administration of leaking to the media "selective and deliberately misleading" information designed to damage Mr Salmond.
He said a tabloid report that Mr Salmond had objected to the release of a further tranche of evidence to the committee "can only have come from the Scottish Government".
The row broke out after Mr Salmond offered to drag Ms Sturgeon's government back to court to help the inquiry obtain key documents that it has refused to hand over.
Mr Salmond won a judicial review last year when Scotland’s highest civil court found that the way the Scottish Government investigated sexual misconduct allegations against him was unlawful and "tainted with apparent bias".
The committee's inquiry was kick-started in March this year when Mr Salmond was acquitted of 13 sex offences at the High Court in Edinburgh.
Ms Sturgeon told parliament at the time that the inquiry could have whatever material it wanted, but her government has since withheld evidence on legal grounds and tried to block witnesses.
Sir Peter, who was permanent secretary between 2010 and 2015, told the inquiry no formal complaints were made against ministers during this period, with issues generally being dealt with "informally".
However, he admitted this approach was only effective "in the short term, sometimes" and he was aware of "concerns" about Mr Salmond's conduct.
He said: “I knew that the former First Minister could display bullying and intimidatory behaviour, yes. Bullying and intimidatory behaviour, I knew he could display those behaviours. I knew the situation we were dealing with.”
Sir Peter said he did not witness any bullying by Mr Salmond, but was “well aware” from conversations with his principal private secretary and others that it occurred.
He said Mr Salmond's office usually ran very well, and staff were highly motivated and excited to be there, but this was occasionally "punctuated" by issues with his conduct. He added: "Did I know about this? Yes, I did.”
Questioned if it would have been appropriate to raise the complaints with Ms Sturgeon, he said: "It would be appropriate in all the settings I've worked to speak with a senior member of the administration concerned, yes."
Asked for the definition of a senior minister, Sir Peter said it would be "somebody with whom I felt such a conversation would be profitable" but refused say whether he spoke to Ms Sturgeon.
John Swinney, the current Deputy First Minister, previously told the committee that some legal and court papers related to the government's investigation into Mr Salmond could not be handed over as an unnamed individual had objected.
Last Saturday's Daily Record reported this was Mr Salmond but Mr McKie told the committee that the relevant correspondence could be made available "on a confidential basis."
He said he wrote to the Scottish Government last month to warn "we would return to court on behalf of our client if they attempted to breach court rulings or undertakings" by providing other information the committee had not requested.
In a separate letter to the SNP administration, he noted the information in the Record article could only have come from this letter, which was marked private and confidential, and demanded that this "clear data breach" be reported immediately to the Information Commissioner's Office.
Ms Baillie said: "It seems that the Scottish Government’s default mode of operation is cloak and dagger. This is not acceptable and must end.”
A Scottish Government spokesman said: "As the First Minister has repeatedly made clear, she looks forward to giving evidence to the committee in due course."
He added: "We have already replied to Levy and McRae to say we have no evidence of any leak of their client’s data or correspondence on this matter from the Scottish Government."