Zebra comment crossing a line: Lib senator

A Labor senator has been chastised over an accusation he likened cabinet minister Michaelia Cash to a zebra.

Liberal senator Linda Reynolds complained to the Senate president on Wednesday about a comment Glenn Sterle made in the chamber.

She was just about to ask the minister for women about domestic violence ahead of White Ribbon Day.

"One of the senators opposite, when the minister stood up, made a highly derogatory comment to the minister about her appearance," Senator Reynolds said.

"I think particularly on this subject, on this day, (he) referred to her as a zebra, in fact, I just think it was highly inappropriate."

Senator Cash was wearing a black and white striped outfit.

Senator Sterle denied the remark was directed at Senator Cash, saying he was just sharing a joke with a colleague.

"I just said: 'What's black and white and eats like a horse?''" he said.

"I didn't mention anything about anyone over there."

Senator Reynolds was having none of it, saying it wasn't the first time the opposition had made disparaging remarks about Senator Cash.

She pointed to Labor senator Doug Cameron's comment earlier this week that Senator Cash needed to hold a male colleague's hand, and another earlier this year calling both women "silly little schoolgirls".

"I hope both senators apologise to minister Cash," Senator Reynolds told AAP in a statement.

"Their comments not only demean them, but all of us."