A “credible” allegation that the identity of a woman who complained about Alex Salmond’s behaviour was disclosed by a Scottish Government official is being investigated, Nicola Sturgeon has confirmed.

The independent adviser to the Scottish Government on the ministerial code, James Hamilton, cleared the First Minister of any breaches over her involvement in the unlawful investigation of sexual harassment complaints about the former first minister.

But he asserted that the claim Mr Salmond’s former chief of staff Geoff Aberdein was told the name of a complainer by a member of the First Minister’s staff in early March was believable.

The account from Mr Aberdein was corroborated by four people who gave evidence to the inquiry, Mr Hamilton confirmed.

In a heavily redacted section of his report, Mr Hamilton states that Mr Aberdein’s recollection of the meeting was “more straightforward” than the “rather complicated” and “elaborate” account of the government official who appears to have denied leaking the name.

Mr Aberdein subsequently informed Mr Salmond and three other people about the woman’s identity being disclosed – former civil servant Lorraine Kay, who worked in the former first minister’s office, former SNP MSP Duncan Hamilton and the SNP’s former communications director, Kevin Pringle.

Although he acknowledged he cannot be “completely certain” about whose account is truthful, Mr Hamilton concludes: “In view of the fact that Mr Aberdein informed these four individuals of the conversation promptly, I believe that Mr Aberdein’s account of what was said by [Redacted] the existence of complaints and the identity of a complainer is credible”.

When asked about the claim during her evidence session of the separate Holyrood inquiry, Ms Sturgeon said: “The account that I have been given has given me assurance that what is alleged to have happened at that meeting did not happen in the way that has been described.”

She suggested that Mr Salmond may have already known the name of one of the complainers “because he had apologised to the person concerned” and had possibly discovered the identity of the other “through his own investigations”.

Asked about Mr Hamilton’s finding that it was “credible” the identity of a complainer was revealed in an interview after the report was published, Ms Sturgeon said: “I understand there is a complaint that’s been made about that which will be taken forward in the proper way.

“Let me, let me be clear about this, Mr. Hamilton has been asked to look at different accounts of meetings and discussions, and he has assessed all of that but what Mr Hamilton was being asked to adjudicate on taking all of that into account, is whether or not I’ve reached the ministerial court and he has been very clear and unequivocal in his conclusion that I did not.”

She then confirmed that there was a government investigation under way but could decline to comment further.

Speaking in her office in St Andrew’s House in Edinburgh, Ms Sturgeon said she was “delighted” and “relieved” that Mr Hamilton concluded she had not committed a breach of the ministerial code.

She also accused the Scottish Conservatives plan to hold a vote of no confidence in her as a “stunt”.

“I’m confident that vote will express confidence in me,” Ms Sturgeon said.

“Remember that the Tories said they would have a confidence vote in me before I uttered a single word of evidence before the parliamentary inquiry.

“They have decided on this issue a long time ago this is a political stunt being brought forward by the Tories tomorrow.”