ACT Labor believes opposition health spokesman Jeremy Hanson will be elected leader of the Canberra Liberals on Monday.
And Attorney-General Simon Corbell says Mr Hanson, pictured, must ''come clean'' about his role in the push to unseat Liberals senator Gary Humphries.
Mr Hanson is the front-runner to replace outgoing leader Zed Seselja in Monday's opposition leadership ballot, while party whip Alistair Coe is considered a strong chance for deputy.
Mr Corbell said on Friday that the opposition health spokesman needed to reveal at what point he knew of Mr Seselja's plans to challenge Senator Humphries and whether or not he agreed to support Mr Seselja's bid in exchange for the party leadership.
''If it is the case that Mr Hanson's going to become the leader of the opposition - it would appear he is the leader-apparent - he needs to come clean with the Canberra community about the terms on which he is becoming leader,'' Mr Corbell said.
''Is it in exchange for his support for Zed Seselja to become the Senate candidate? ''When did he know about this deal?
''Is it the case this was being talked about in the Liberal Party well ahead of the rank and file knowing about it?
''And has he said he will support Zed in return for getting Mr Seselja's vote to become leader of the opposition.''
Mr Corbell described Mr Seselja's challenge as an ''extraordinary act of vanity'' and the push to unseat Senator Humphries was a ''coup''.
''I think that's the big question - was this a Plan B before the election? That's what Hanson has to answer to as well. ''Was there a Plan B?
''You have to ask the question whether or not he [Mr Hanson] was complicit in all of this.
''It's up to him to dispel that.''
Neither Mr Seselja nor Mr Hanson chose to respond to Mr Corbell's comments, but, representing the Liberals, Mr Coe said: ''Unlike the Labor Party, the Liberal Party does not have factional deals, captain's picks or access to Eddie Obeid's ski lodge''.