The family of Carl Sargeant has released correspondence indicating he was facing allegations of "unwanted attention, inappropriate touching or groping" at the time of his death.
The family confirmed the Labour politician was unaware of the exact details of the allegations at the time of his death, and said his distress at being unable to defend himself properly meant he was not afforded "common courtesy, decency or natural justice".
In a letter and email sent to the Labour Party on Monday, Mr Sargeant's solicitor Huw Bowden made clear that the Alyn & Deeside AM "categorically denied" any wrongdoing and appealed to the party to provide details of the accusations against him.
He noted the party had confirmed that no "parallel investigations" - such as a police inquiry - were being conducted.
Writing the day before the 49-year-old's death, Mr Bowden warned that the case was causing Mr Sargeant anxiety and distress and that any delays in concluding the party's investigation would be "prejudicial ... to his physical and mental well-being".
Mr Bowden complained that broadcast interviews by Carwyn Jones, in which the Welsh First Minister said he had been informed of "a number of incidents" relating to Mr Sargeant's behaviour with women, were prejudicing the inquiry.
A family spokesman said: "Up to the point of his tragic death on Tuesday morning Carl was not informed of any of the detail of the allegations against him, despite requests and warnings regarding his mental welfare.
"The correspondence also discloses the solicitor's concern that media appearances by the First Minister on Monday were prejudicing the inquiry.
"The family wish to disclose the fact that Carl maintained his innocence and he categorically denied any wrongdoing. The distress of not being able to defend himself properly against these unspecified allegations meant he was not afforded common courtesy, decency or natural justice."
In his email, Mr Bowden said that it appeared a "large number of people" had spoken to the complainants without Mr Sargeant even being informed of who they were.
"There appears to be a very real possibility that the evidence of the witnesses is being manipulated and numerous conversations with the witnesses by various members of the First Minister's Office at the very least must create uncertainties about the credibility of any evidence," he wrote.
Mr Bowden demanded a full log of any contacts with witnesses and complainants.
In his letter he stated: "We would make it clear at the outset that our client categorically denies any allegation that he has acted in a manner that is either prejudicial or grossly detrimental to the party.
"We are led to believe that the allegations concern conduct that you described as our client having acted towards others in such a way as alleged to be 'unwanted attention, inappropriate touching or groping'. We make it clear that any such allegations are categorically denied."
He added: "We are sure you appreciate the anxiety and distress being caused to our client, particularly as he is yet to receive any details of the allegations that have led to the decisions taken to date by the First Minister of Wales and the Labour Party head office."
Noting that a first hearing for the inquiry was not scheduled until January 16, Mr Bowden said: "With the Christmas period intervening ... the ongoing delay is both prejudicial to the preparation of our client's case, but also to his physical and mental well-being."
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