United Australia Party senator Brian Burston has launched defamation action against One Nation leader Pauline Hanson and former staffer Wendy Leach.
Senator Burston said he denied any and all allegations of sexual harassment and mistreatment made against him by Ms Leach and repeated by Senator Hanson, along with other "defamatory and false statements".
"I have no recourse but to pursue damages to bring Ms Leach and Ms Hanson to account for these reckless and plainly false comments clearly designed to cause me personal, professional and political damage,'' he told AAP on Wednesday.
Comment was being sought from Senator Hanson.
Senator Burston said he would be seeking "substantial damages".
"These statements have caused me extreme embarrassment and humiliation. These allegations have strained my relationships with my family, friends and professional colleagues."