Speculation is mounting that the prime minister could reshuffle his front bench before Christmas.
The Nationals are understood to be pushing for five spots in cabinet after the elevation of Bridget McKenzie as party deputy leader.
Malcolm Turnbull may boost the size of his cabinet from 21 to 22 to accommodate the junior coalition partner, which has had a morale boost in Barnaby Joyce's by-election win.
Attorney-General George Brandis, who has been the subject of speculation for months that he will take up the role of high commissioner in London, says his future is in the prime minister's hands.
His portfolio duties will be whittled down with the creation of a new Home Affairs ministry to be headed by Immigration Minister Peter Dutton.
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Industry Minister Arthur Sinodinos is fighting cancer and the special minister of state portfolio needs to be filled after Scott Ryan became Senate President.
One complicating factor for a broad reshuffle is constitutional questions surrounding the eligibility of assistant minister David Gillespie, who is due at the High Court on December 12.
The prime minister is also understood to be keen to wait for the December 16 by-election in Bennelong before announcing any frontbench changes.
