Independent senator Jacqui Lambie is expected to outline the number of veteran cases that come through her office at an inquiry into defence suicides.
She called for a royal commission into the "toxic culture" of defence during her maiden Senate speech in 2014, saying the highest form of public inquiry was the only way to remedy the "gross injustices".
Senator Lambie will appear at a royal commission hearing on Tuesday.
The hearings, which wrap up at the end of March, will be the last opportunity for the inquiry to cross-examine witnesses before handing down its final report in early September.
Giving evidence in August 2022, Senator Lambie spoke about years of legal battles with the Department of Veterans' Affairs in her push for compensation following her service.
She said the department conducted surveillance at her Devonport home in the early 2000s, and a camera was "put over her back fence".
Defence told the royal commission on March 5 the department did not have a reliable data set for sexual misconduct.
The department's Sexual Misconduct Prevention and Response Office will also give evidence on Tuesday.
Defence Minister Richard Marles and Veterans' Affairs and Defence Personnel Minister Matt Keogh last week confirmed they were concerned with issues of culture and the availability of data.
A group of veteran organisations, including Mates for Mates and Women's Veterans Australia, will face the inquiry.
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