New Liberal senator for WA sworn-in

Finance Minister Mathis Cormann's former COS, Slade Brockman, is sworn in.

After losing a string of senators, federal parliament's upper house is starting to refill its seats with the swearing-in of a new Liberal senator.

Slade Brockman - the former chief of staff for Finance Minister Mathis Cormann - is filling the casual vacancy left by West Australian Chris Back who retired in June.

The Senate still has two seats to fill following the resignations of Greens senators Scott Ludlam and Larissa Water over citizenship issues.