Carwyn Jones has asked the Welsh Government's top official to begin setting up an independent inquiry to examine his handling of the Carl Sargeant case.
A spokesman for the Welsh First Minister said Mr Jones believes a senior QC should carry out work to examine his "actions and decisions" in relation to the former assembly member, who was found dead on Tuesday.
Mr Sargeant, 49, is understood to have taken his own life four days after being removed from his role as cabinet secretary for communities and children and suspended from the Labour party over allegations of "unwanted attention, inappropriate touching or groping".
On Thursday Mr Jones said he acted "by the book" in his handling of misconduct claims, after he faced anger and calls to resign after it emerged that Mr Sargeant had not been given full details of the claims against him.
A spokesman for Mr Jones said: "Further to the First Minister's comments yesterday about the need for independent scrutiny of his actions and decisions in relation to Carl Sargeant, he agrees that there should be an independent inquiry and it would be proper to ask a senior QC to lead that work.
"To ensure this happens separately from his office, the First Minister has asked the Permanent Secretary to begin preparatory work for this inquiry, and to make contact with the family to discuss the terms of reference and the identity of the QC.
"It is our understanding that such an inquiry should not take place before the outcome of a coroner's inquest - but we will take further advice on this matter."
Mr Jones had been under mounting pressure to launch an independent inquiry, with Mr Sargeant's family adding to the criticism shortly before the First Minister's announcement.
Mr Sargeant's family said there had been "serious failings" in the way the situation was handled.
Welsh Tory leader Andrew RT Davies and figures from within Mr Jones' own party had called for the First Minister to announce an investigation.