The battle between Michael O'Brien and Matthew Guy to lead the remnants of the parliamentary Liberal Party will be over in a matter of days, with the former planning minister expected to have the numbers.

Outgoing attorney general Robert Clark announced that a new leader would be decided by the Liberal Party at a meeting this week.

Matthew Guy is tipped to be the next leader of the parliamentary Liberal Party.

Senior Liberal sources on Sunday told Fairfax Media that the former Planning Minister "had the numbers", despite the fact that former federal treasurer Peter Costello was lobbying on behalf of O'Brien, his former staffer.