Management of a defence investment program worth $134.1 billion which includes new weapons, systems and infrastructure is only "partly effective" and failed to establish a framework for public reporting.
Auditor-General Grant Hehir reviewed the Department of Defence's processes for managing its Integrated Investment Program and transparency about the project costs in two public reports since 2016.
The Integrated Investment Program contains the department's proposed capability projects and was developed in 2015.
The value of new project proposals approved under the program from 2016 to 2022 is $134.1 billion.
The report, released on Tuesday, found administration of the Integrated Investment Program since 2016 has been "partly effective".
It revealed while Defence had set up a "largely effective governance, control and approval framework for the management of the program," it had failed in establishing a framework to guide its public reporting on the program.
The auditor-general made six recommendations to improve Defence's governance for the management of the program, and its public reporting.
The department agreed to five of the recommendations, but rejected one that it state progress on its plans in its public reports on the program.
This would include showing projects cancelled, amalgamated, delayed, or changed in scope or cost.
"The accuracy and completeness of information provided to the parliament, public and industry on major government investment programs is essential to supporting transparency and users of the information," the report found.
In its response to the auditor-general, Defence said it kept the government, public and industry informed through a range of measures.
"These approaches include submissions to government, government committee hearings, audits and reviews by the ANAO, Industry briefings and media releases," the statement reads.
"Any future public release of the Integrated Investment Program will be subject to consideration by government and will consider national security implications as well as commercial sensitivities."
Meanwhile, Defence Minister Richard Marles will travel to the United States next week for discussions with his US and UK counterparts.
He said cooperation on defence projects, including nuclear-powered submarines, would be on the agenda of the first AUKUS defence ministers' meeting.
"We look forward to what will come from this because of the opportunity that AUKUS does provide for building Australia's military capabilities and, through that, providing huge opportunities for the Australian defence industry to contribute to that," he told a forum in Canberra on Tuesday.
Australia plans to acquire the nuclear-powered vessels under the AUKUS security partnership with the US and UK to replace the nation's ageing Collins Class fleet.
The minister expects to announce the type of submarines Australia will acquire in March.