With caveats depending on locale/state:
Queensland
On multi-lane roads, if the posted speed limit is 90km/h or more, or if the road has a ‘keep left unless overtaking’ sign, you must not drive in the right-hand lane unless you are:
overtaking
turning right
making a U-turn
avoiding an obstruction
driving in congested traffic
using a special purpose lane that you are allowed to be in.
Hold a seniors card and stick to the posted speed limit religiously without regard for Speedo errors or the fact your car is on larger tyres than specified*
Drivers are allowed to overtake on the left on all multi-lane roads.
*this line may have been made up!