An inquiry into whether details of Carl Sargeant's sacking were leaked before he was told has been ordered by Wales' first minister.
Mr Sargeant was found dead four days after being sacked by First Minister Carwyn Jones and told allegations had been made about his personal conduct.
Former minister Leighton Andrews said he believes others were told of his sacking before it happened.
Mr Jones has asked the permanent secretary to investigate the claims.
A spokesman for the first minister said: "Whilst no evidence has been found to support these allegations, the first minister has asked the permanent secretary to look into the matter."
Mr Sargeant, who was the AM for Alyn and Deeside, maintained he was not told the details of the allegations against him.
He was sacked from his job as cabinet secretary for communities and children amid allegations he had "touched or groped" a number of women.
Mr Jones has said he had no alternative but to remove Mr Sargeant from his cabinet.
In a blog post, Mr Andrews said he believes a journalist, a Labour AM and a Labour MP were aware of what was about to happen in advance of the reshuffle.
He wrote: "Were the leaks to the Labour AM, the Labour MP and the journalist direct from the 'Fifth Floor' - the Ministerial Floor - or were they from intermediaries who had themselves had information leaked to them?
"If so, who were the intermediaries and what interest did they have in leaking the material, and why was it leaked to them and by whom?
"At the end of the day, information must have been leaked from someone - or some people - on the Fifth Floor.
"The permanent secretary should conduct a full leak inquiry, if she isn't doing so already, into all calls, texts and emails sent by relevant people on the day of the reshuffle and the days leading up to it.
"Someone, or some people, leaked the news about Carl Sargeant's sacking. This has never happened before in any Welsh Government reshuffle. It is unprecedented. So who leaked? And to whom? And how many people knew?"
The Permanent Secretary needs to get a grip of this situation and provide answers. All questions and information requested should be acted upon, answered and released immediately. Any delay in these circumstances is completely unacceptable. https://t.co/KFKFE29800— Andrew RT Davies (@AndrewRTDavies) December 4, 2017
Plaid Cymru AM Adam Price said he would be asking the Welsh Government to conduct "an internal investigation" into the leak allegations.
And Welsh Conservatives leader Andrew RT Davies tweeted: "Any delay in these circumstances is completely unacceptable."
Meanwhile, an independent inquiry led by a QC will look into the circumstances leading up to Mr Sargeant's death.
A separate inquiry is looking into whether Mr Jones broke the Ministerial Code in addressing questions - raised by Mr Andrews - about a "toxic" culture within the Welsh Government dating back to 2014.
Mr Andrews left the Welsh Government in 2016 after losing his Rhondda seat.
Analysis by BBC Wales political editor Nick Servini
And so we have another inquiry in response to the death of Carl Sargeant.
This time it is about who knew what in the days and hours leading up to Friday November 3 when Carwyn Jones reshuffled his cabinet, and sacked Carl Sargeant.
Every Welsh Government cabinet reshuffle I have covered is accompanied by the inevitable dose of speculation about timing and content, particularly among political journalists, back benchers and opposition parties.
On this occasion people were asking the question about whether veteran ministers like Carl Sargeant would hold on to their portfolios, because there were new faces within Labour ranks that Carwyn Jones wanted to bring into government.
Late morning, on the date of the reshuffle, a BBC journalist received a tip off that Carl Sargeant would lose his job and tweeted to that effect shortly afterwards.
But what is unclear is whether Mr Sargeant had already been told by that point.
Cabinet reshuffles have variable outcomes, but they usually have the same characteristics of speculation and rumour, and this was no exception.
The difference here is that it has been caught up in the raft of inquiries following Mr Sargeant's death.