Attorney-General George Brandis will reportedly quit the Senate and become the next UK High Commissioner.
The decision for him to replace Alexander Downer is expected to be confirmed in a reshuffle by Malcolm Turnbull sometime this week, several reports suggest on Monday.
The prime minister is also understood to be considering returning former minister Sussan Ley to the ministry.
Liberal MP Tim Wilson could not confirm Senator Brandis' move but conceded there would be a reshuffle this week.
"The reality is governments always need a bit of a refresh mid-term," he told Sky News.
New deputy Nationals leader Bridget McKenzie is expected to be promoted to cabinet in the shake-up, to take the spot left by Fiona Nash who was disqualified for being a dual citizen.
Scott Ryan's move replacing Stephen Parry as Senate president, after he was also disqualified, has created another cabinet vacancy.
There are also questions over the ministerial future of Arthur Sinodinos, who is battling illness.
