A routine annual report from the Inspector-General of the Australian Defence Force for the 2020-21 financial year, which is typically released in the months following the year's end, remains unavailable despite passing its May tabling deadline.

The document is expected to contain information regarding the watchdog office's actions following the public release of the Brereton report into war crime allegations during Australia's involvement in Afghanistan along with other contentious issues.

But a spokeswoman for Mr Dutton told The Canberra Times in March the report's release wasn't delayed, adding that it had to be tabled in the lower house by May 9.

The Inspector-General's office advised Mr Dutton he must present the report on, or by, that date, according to reasons outlined in a refused freedom of information request for an explanation lodged by The Canberra Times.

In the fortnight leading up to polling day, the Defence Minister's office has again refused to release the report, explaining it was in "caretaker" mode.

A spokeswoman said on Tuesday it couldn't be presented to the lower house because it was in the caretaker period and Parliament wasn't sitting.

However, the tabling office confirmed mid-week it had not received a report and that there was no barrier to ministers presenting reports out of session.

The unreleased Inspector-General of the ADF's report covers the period between July 2020 and June 2021, which includes the period leading up to and following the public release of the Brereton report.

It's also expected to include information relating to a separate report by the watchdog into rising sexual assault cases and issues raised about the transparency of military justice outcomes for survivors.

Independent senator Rex Patrick said Mr Dutton's refusal to release the report ahead of the federal election was another reason voters wanted to see a federal integrity commission introduced.

"This is the very secrecy that has caused people to lose trust in this government. The issues covered in this report are important and the public have a right to know about them," the South Australian senator said.

"It's blatantly untrue that you can't table a document out of session.

"We won't know whether this is just a defence minister that hasn't kept up with his work or whether the withholding of it is deliberate, until such time as we've seen the content.

"It just raises suspicion amongst the public."

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Neil James, executive director of the Australia Defence Association, said there would be "considerable concern" if it still wasn't released by the end of June - more than a year after the reporting period's end.

"For transparency, for resolving problems in the long run, you're always better off publishing reports," Mr James said.

"If it isn't [released] within a month, that would be a cause for considerable concern.

"These things are always better off exposed to sunlight."