Attorney-General Christian Porter faces being called to testify on his unprecedented exercise of powers to block the Auditor-General from reporting his conclusions on a $1.3 billion defence contract.
Key independent senator Rex Patrick, who has been embroiled in a 15-month legal battle with the federal government to get access to the full audit report, plans to subpoena Mr Porter to appear in court to explain his reasons for forcing the Auditor-General to censor his findings.
Senator Patrick, who is a member of Parliament's Joint Committee on Public Accounts and Audit, told the Canberra Times he was disturbed by the Attorney-General's decision.
"I think he (Mr Porter) has exercised his power improperly.
"I think he has got to be heard on why those parts of the report had to be redacted."
Auditor-General Grant Hehir sounded the alarm after the Attorney-General in 2018 issued a section 37 certificate that called for information in an audit of the contract for Thales to build more than 1000 light combat vehicles, including the audit's conclusions, be omitted from the final report on defence, security and international relations grounds.
Mr Hehir said the Attorney-General's "unexpectedly broad" interpretation of his powers posed an "ongoing risk" to his independence and the work of the Australian National Audit Office.
The audit's aim was to assess the effectiveness and value for money of the contract, which called for Thales to build 1100 of its Hawkei vehicles and 1058 accompanying trailers at its Bendigo facility.
A parliamentary inquiry into the Attorney-General's decision found that the audit report did not disclose any classified national security information.
But Thales Australia launched legal action to have the report blocked and, when that failed, the company then asked the Attorney-General to intervene, Senator Patrick said.
The Attorney-General based his intervention on the grounds that sections of the report would affect "sovereign industrial capability".
But the Auditor-General told the inquiry that, "the work undertaken in this audit wasn't unusual...nor were the conclusions drawn from it".
A full version of the audit report was sent to Prime Minister Scott Morrison, so Senator Patrick submitted a Freedom of Information request in order to gain access, which was denied.
The matter has been tied up in the Administrative Appeals Tribunal ever since, and has also been reviewed by the Australian Information Commissioner.
Senator Patrick said the government had mounted multiple defences, including parliamentary privilege and cabinet-in-confidence, to block access.
Constitutional law expert Professor Anne Twomey has weighed in on the matter.
"For parliamentary privilege to be used in such circumstances to uphold the effectiveness of the certificate and prevent Parliament from being able to receive and debate the full report would be a travesty of justice," Professor Twomey wrote in a paper published late last month.
Senator Patrick said the matter could yet end up in the High Court, but was confident of success and planned to then launch court action to compel the Attorney-General to explain his actions.
The Centre Alliance senator said the issues at stake were "critically important" because of Auditor-General's pivotal role played in holding government to account.
"We need to be alert to any attempt to inhibit the auditor or reduce the independence of the Auditor-General," he said.