Almost 32,000 non-public service employees were given government security clearances by the Defence department in the past two years, pointing to an explosion of high-level outsourced work at the department.

The department says it doesn't track the number of contractors working on its projects, but the number of clearances sponsored by the department shows the number of contractors now dwarfs the number of public service employees at Defence.

The project to replace Australia's ageing submarines has contributed to the uptick of contractors working on Defence projects. Credit:Department of Defence

Not all contractors and consultants need security clearances, meaning the true number of outsourced workers is likely to be higher than the number of clearances.

In response to a question on notice, Defence said it sponsored 16,272 security clearances for non-APS staff in 2016-17, and 15,653 clearances in 2017-18. In the last financial year the department's average staffing level was 17,500, which was cut by 1127 jobs in the most recent budget. These numbers don't include uniformed members of the military.