Darren Chester, who served as minister for veterans' affairs and defence personnel until July 2021, came under sustained attack during Wednesday's hearing of the Royal Commission into Defence and Veteran Suicide.

In a series of terse exchanges with the commission, the former minister defended the government's failure to act on series of reforms recommended by the Productivity Commission in December 2019.

Counsel Assisting, Peter Singleton, asked Mr Chester if he could explain why, in the three years since the commission had delivered its report, there had been no commitment to any of the reforms.

Mr Singleton said this included three key recommendations to "harmonise" the highly complex pieces of legislation identified as the primary cause of the 60,000-strong backlog of claims at the Department of Veterans' Affairs.

Mr Chester conceded no serious attempts were made to adopt a raft of reforms during his time as minister from March 2018 to July 2021.

In the same period the backlog of Department of Veterans' Affairs claims ballooned from 12,000 to 60,000.

Pressed repeatedly by Mr Singleton about what steps had been taken, Mr Chester struggled to explain why work had not progressed beyond his request for a "legislative roadmap" in May 2021, two months before he left the portfolio.

"The ultimate conclusion must be, mustn't it ... with what has been achieved in three years (the) government's failed in its duty to veterans?" Mr Singleton said.

Asked if he accepted the "sheer complexity" of the DVA claims system had led to mental health problems for some veterans, Mr Chester said that had been a concern for him as minister.

But he was unconvinced there was a "direct causal link" with the high suicide rates among veterans, even though "having a system which is so complex and confusing to navigate can add to the anxiety and the stress".

"All I'm saying is I can't point you to a case where I can say a single individual veteran went down a pathway of suicidality as a direct result of a complex system," Mr Chester said.

He explained how the DVA now allows mentally ill veterans access to medical treatment while their claim was still being processed.

He added that the fast tracking of mentally ill veterans claims had been implemented following the 2017 suicide of 32-year-old Afghanistan veteran, Jesse Bird.

"You are obviously familiar with (the Jesse Bird case), yet you stated in a considered way that you can't point to one case where the system may have contributed to suicidality," commission chair Nick Kaldas said.

"Clearly that is not the case but I'm just wondering can you understand ... that sort of approach or answer is often seen by families who are grieving as an attempt to diminish or minimise the harm that the broken system does to families?"

Mr Chester: "Sorry, commissioner".

Mr Kaldas: "Can you acknowledge that?"

Mr Chester: "I hope I didn't suggest in my evidence that the complexity of the system couldn't contribute".

" I was saying I couldn't think of a case where the only cause of people self-harming or suicide was delays in the system. I hope I didn't sound in any way unempathetic to ... Mr Bird's case."

The chief of Defence, Angus Campbell, is due to start giving evidence on Thursday.

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