Colin Barnett will step into the role of Treasurer in the lead-up to a Budget for the second time in four years to cover for Troy Buswell, who has taken three weeks’ personal leave.
The Premier’s office has confirmed Mr Barnett had taken on Mr Buswell’s Treasury and Transport portfolios until at least March 14.
The Liberal Party room was told last Tuesday that Mr Buswell was away but would return the following day.
The Labor Party was told Mr Buswell was sick when it granted him a “pair” from Parliament and, as convention dictates, drop one of its numbers during votes.
Mr Buswell did not return to Parliament on Wednesday or Thursday and his office told media he would be on leave all of this week.
That has since been extended to at least the end of next week.
A spokeswoman for Mr Buswell said he was on “personal leave”.
“The Premier is acting and Budget preparations are continuing,” she said.
Mr Barnett has taken over Budget preparations at short notice before.
In 2010 he acted as Treasurer while Mr Buswell headed to the backbench after he agreed to pay back entitlements he claimed during a visit to Albany with former partner and Greens MP Adele Carles.