Thousands of files, some of them "top secret", have been found in two old filing cabinets, bought at an auction in Canberra.

The documents were passed on to the ABC, which has published some of the contents this week.

The files cover five governments over the last ten years.

An audit by the office of the prime minister and cabinet uncovered the loss of the files.

Thousands of files have been found in old cabinets bought at an auction in Canberra.

One of the lost files showed former Prime Minister Kevin Rudd was warned of risks with is pink bats insulation scheme.

Four young workers died during installation.

Another file, made public yesterday, revealed discussions by Tony Abbott's cabinet about a possible budget move to axe welfare payments for those under 30 years.

Former Prime Minister Kevin Rudd.

Tony Abbott cabinet files were made public.

Among the treasure trove of Government secrets was the fact that an audit revealing the Australian Federal Police lost almost 400 national security files over five years.

One file shows how almost 200 top secret, code worded, sensitive documents were left in the office of then minister Penny Wong when Labor lost the 2013 election.