Asio officers secured thousands of sensitive government cabinet documents at ABC offices in Canberra and Brisbane after they were found in a locked filing cabinet bought from a second-hand shop.

The Department of Prime Minister and Cabinet 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.

Around 1am on Thursday, Asio officers brought a safe to the public broadcaster’s bureaus at Parliament House and in Brisbane so the documents could be kept securely.

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.

The deputy prime minister, Barnaby Joyce, said the person responsible for losing the documents will have serious questions to answer.

“Obviously someone’s had a shocker and the investigation will find out exactly how this happened,” he told ABC radio on Wednesday.

Cabinet papers are legally supposed to remain secret for 20 years after their production.

“In the process of running a country, there are things which go awry. This is one of them,” Joyce said.

The ABC said it had chosen not to publish many of the documents because of their classified nature.

The former prime minister Tony Abbott said he believed a junior or mid-ranking departmental officer was to blame and insisted they “pay a price”.



“Not so much a cabinet leak as a leaked cabinet – that seems to be the problem,” Abbott told 2GB radio.