A watchdog has panned the federal government for using extremely rare powers to hide vast swathes of an audit into a $2.2 billion military deal.
Auditor-General Grant Hehir spent 18 months examining Defence's procurement of 1100 locally-built Hawkei light protected vehicles from French contractor Thales.
Earlier this year, Attorney-General Christian Porter suppressed large slabs of his audit.
Mr Porter said publishing the contents would prejudice Thales' commercial interests and threaten Australia's security, defence or international relations.
His decision to issue the suppression certificate by drawing on never-before-used powers is now being investigated by a parliamentary inquiry.
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In a damning submission to the inquiry, the auditor-general has revealed the material suppressed from his report was worked through with the Department of Defence to ensure there were no national security threats.
Mr Hehir said he remains unaware why the national security concerns were used to justify the omissions, adding that the treatment of sensitive information regularly arises in the context of Defence auditing.
"It would be of concern if this certificate set a precedent for government to regularly suppress elements of an auditor-general's conclusion and ANAO [Australian National Audit Office] analysis in a public report," Mr Hehir wrote to the committee.
"The 2018 certificate establishes a precedent which, if repeated, may affect parliament's scrutiny of the executive by limiting the auditor-general's independent and public reporting to the parliament."
