New stats show that the federal public sector is smaller than it has been anytime in the last decade.

The latest APS Statistical Bulletin shows the number of Australian public service employees dropped by 1.8 per cent to 150,489 in the 12 months to December 31.

This is its lowest level since 2007, and is down from a peak of 166,582 people in 2011.

There were 2767 fewer employees in December 2017 than December 2016, and a drop in casual staff, from 9217 to 6967 staff.

The new Home Affairs super department is now the fourth largest agency, with 14,355 staff.

The Department of Human Services remains the largest, followed by the Tax Office and Defence.

The number of women in senior roles within the public service has increased, with women now taking up 44 per cent of SES roles and 45 per cent of EL2 roles.