Pauline Hanson could be referred to the Senate's powerful privileges committee over her treatment of former One Nation senator Brian Burston.
Senate President Scott Ryan gave the green light for Senator Burston to move a motion on Wednesday to refer her over pressing him to resign from the upper house.
If the matter is referred, an inquiry will look into whether Senator Hanson had interfered with the Clive Palmer-aligned Senator Burston's duties, potentially putting her in contempt of parliament.
Senator Hanson and her former colleague had a bitter falling out after she reneged on a deal with the government to support company tax cuts.
Senator Burston said he wanted to keep his word on the agreement, leading to him being kicked out of the party.
He also refused to resign from parliament after Senator Hanson asked him to quit.
The United Australia Party recruit's motion referring Senator Hanson to an inquiry will investigate whether there was improper interference with the performance of his duties as a senator or if he was penalised for his conduct as a senator.
Senator Ryan said whether the issue warranted investigation as a possible contempt was a question for the upper house.
"I have determined that the matter should have precedence as a matter of privilege," he said.
But he noted the committee was generally reluctant to intervene in internal party matters, but did not close the door on the possibility of contempt.
Contempt of parliament can attract a fine or even jail if the offence is found to be serious enough.
