The Department of the Prime Minister and Cabinet has admitted the thousands of 'top secret' documents bought from a second-hand shop in Canberra came from them.
In a statement, the department's secretary Martin Parkinson said it was "now reasonably evident that the cabinets and documents which are the subject of the AFP investigation, came from the Department of the Prime Minister and Cabinet".
"While it remains unclear, it is likely this occurred some time ago," he said.
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"This casts the Department in a poor light and this failure has implications for the rest of the Australian Public Service.
"Accordingly, while the AFP investigation is ongoing, I will be instigating a review of the Department’s security procedures, practices and culture, including the implications for the Australian Public Service."
Mr Parkinson said the AFP investigation into how the documents ended up in two filing cabinets was still ongoing.
ASIO took possession of the thousands of sensitive government files on Thursday evening after the ABC and the department agreed on the securing and return of the documents.
The national broadcaster said the transfer did not compromise the source of the cabinet files.
The department launched an urgent investigation on Wednesday after the ABC revealed it had obtained papers covering details of five federal government cabinet meetings over a decade.
The trove, some classified "top secret", was sold cheaply at a second-hand shop in Canberra, which stocked ex-government furniture.
The filing cabinets were unlocked with a drill months later.
