Carwyn Jones 'caused considerable distress' to Sargeant family
The lawyers of Jack Sargeant have written a strongly-worded letter accusing First Minister Carwyn Jones of causing "considerable distress".
Mr Sargeant's father Carl was found dead in November, four days after being dismissed from the cabinet.
An inquiry into how Mr Jones handled the sacking will be led by Paul Bowen QC, but has not yet begun.
Asked whether his manner had caused distress, Mr Jones told BBC Wales he could not see how that can be the case.
On the eve of the Welsh Labour conference, Jack Sargeant's lawyers said in a letter to Mr Bowen that the first minister's manner was causing "considerable distress to our client and his family".
They added: "The inescapable fact here is that someone sadly has lost their life, a much loved family member, and due process must be followed expeditiously to enable to those closest to him to find some closure."
Later, interviewed by BBC Wales, Jack Sargeant's lawyer Neil Hudgell, said: "It's a culmination of a series of frustrations over the delay to the start of the inquiry."
He said the process "seems to have stalled".
"Our thoughts very much are that it's been de-humanised within the first minister's office, there's some game-playing going on and some deliberate stalling tactics."
Asked about the letter's release on the eve of the Welsh Labour Party conference in Llandudno, Mr Hudgell said there had been "a degree of co-incidental timing" in light of this week's developments in the assembly.
"There might be some cynicism because it's so close to conference but there's been a number of important events this week, a number of comments made that the family just find unacceptable," he said.
Carl Sargeant was dismissed from the cabinet after being subjected to a Labour Party inquiry into allegations of "unwanted attention, inappropriate touching or groping" when he died.
Mr Bowen was appointed in January to lead the independent inquiry into Mr Jones's handling of Mr Sargeant's sacking but the inquiry has yet to start.
Speaking at a school in Llandudno Junction, Mr Jones told BBC Wales he had not seen the letter.
"I think it's in everyone's interests that any issues are resolved as quickly as possible in order for things to move forward," he said.
When asked about the accusation that his manner has caused distress to the family of Jack Sargeant, he said: "I can't see how that can be the case."
Earlier this year Jack Sargeant was elected to represent his father's former seat of Alyn and Deeside in the assembly.
The letter comes at the end of a week where the Conservatives failed in a bid to publish a separate report into whether Carl Sargeant's sacking was leaked in the days before a cabinet reshuffle.
It found no "unauthorised" leaking of information on his sacking but its full details were withheld over fears about the confidentiality of witnesses.
Mr Jones threatened legal action against the assembly over the attempts to publish the report.
He was also cleared of any wrongdoing over allegations he misled the assembly over claims of a bullying culture within the Welsh Government.
Welsh Conservative leader Andrew RT Davies said the first minister's judgement had "come under considerable scrutiny in recent days" and that the lawyers' letter would "only add to the growing pressure his leadership is under".
Mr Davies warned Mr Jones against kicking Mr Bowen's inquiry "deep into the long grass".
Analysis by Nick Servini, BBC Wales political editor
The significance of this letter is all wrapped up in the timing.
The shadow caused by the death of Carl Sargeant was always going to be in the background of what promises to be a packed Welsh Labour conference but this ensures it remains front and central.
From the perspective of the family, there is clearly intense frustration that the main inquiry into the circumstances surrounding his sacking has not even started.
There is difficulty for the Welsh Government too.
Even if ministers share that frustration, no-one can be seen to be meddling in such a highly sensitive area.