Labour MP Louisa Wall is calling for Act leader David Seymour to "man up" and apologise.
It comes after Seymour called Green MP Golriz Ghahraman a "menace to freedom".
It's understood to have escalated threats made against Ghahraman, who has now been allocated a security escort.
Wall is part of a cross-party group of women in Parliament urging Seymour to say sorry.
"He should be not ashamed but at least have the capacity to reflect and say, 'what I have said has done more damage'," she said.