A former Australian soldier was “humiliated and degraded” by military personnel in an interrogation over her sexuality in the 1980s, a royal commission investigating defence and veteran suicide has been told.

Public hearings at the royal commission in Sydney this week are taking evidence from those in the ADF community who have had suicidal ideation, and family members of those who have taken their lives.

The inquiry came about after Prime Minister Scott Morrison declared last year he would not block a move to finally examine the issue of ADF and veteran suicides.

Yvonne Sillett, a former serving army member, who is openly gay, told the inquiry on Monday that in 1988 she was called to meet superiors over her security clearance, as part of a “witch hunt” against homosexual ADF personnel.

The meeting was in fact a three-hour interrogation during which she was “broken down”, “treated like a criminal”, and learned that she had been followed for several months on trips with friends and nights out, Ms Sillett said.

The purpose of the meeting, she said, was to extract from her an admission of homosexuality, which was viewed by the army at the time as a “national threat”.

“I knew that would be the end of my career and my dream,” Ms Sillett told the inquiry, describing the treatment by the army as “humiliating and degrading”.

Ms Sillett, who at times choked back tears giving her testimony, said she took an honourable discharge in 1989 after experiencing suicidal thoughts.

She was very close to taking her life, but managed to pull through thanks to her partner at the time who supported her so she could “tell her story” at the inquiry.

“I knew nothing else, I didn’t have a plan B,” Ms Sillett said.

In the years since, the “trail-blazing” veteran has formed an organisation to support LGBTI+ members of the defence force, but is still waiting for an apology.

“That’s what I’m fighting for, and that’s why I’m here today,” she said.

“No one really wants to listen or take responsibility for the way we were treated.”

Earlier, counsel assisting the royal commission, Peter Gray QC, said the inquiry would address issues of urgency, including delays in processing ADF claims, describing this “backlog” in claims as the focus of the hearings.

He described the backlog as “unacceptably high” and said it had greatly increased since March 2019, with the time taken to process some claims at the Department of Veteran Affairs doubling in two years to an average of around 200 days.

Commissioner Nick Kaldas, in opening remarks, said that his team had so far conducted around 40 private hearings with those in the veteran community, and had received over 250 applications for private sessions from across Australia.

The inquiry had issued over 150 notices to the Defence Department, DVA, and other bodies, resulting in more than 320,000 pages of material to review, he said.

It had also received more than 1100 submissions from a range of people, ex-service organisations and experts.

In addition to ADF members and veterans, witnesses due to testify include DVA personnel, staff from consulting firm McKinsey and medical experts.

Compared with the general population, suicide rates are 24 per cent higher for ex-serving men and double for ex-serving women, according to federal government data.

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