Senator Nick Minchin will on Monday step down as leader of the Liberal Party in the Senate.
Senator Minchin announced in March he was quitting federal politics and would not contest the next election.
He stepped down from the shadow ministry but remained as the opposition's Senate leader.
However, Senator Minchin announced on Sunday he will also forsake that role at a meeting of his Liberal upper house colleagues on Monday.
"It has been my privilege to have been the Liberal Senate leader for four years - two as leader of the government in the Senate, and two as leader of the opposition in the Senate," he said in a statement on Sunday.
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"I have enjoyed extraordinary loyalty and support from coalition senators in my role as leader, for which I am enormously grateful."
Senator Minchin wished the Liberal Senate leadership team well in the lead-up to this year's poll.
