Ardern said she spoke with Mallard on Wednesday morning.
"He retains my overall confidence; however I have expressed serious concerns to him about the manner in which he conducted himself in the House last night.
"It did not meet the standards I expect. Nor do I consider it to have met the needs of the victim in this situation. The Speaker acknowledges he did not meet his own standards either."
Ardern also slammed the Opposition's "inappropriate" behaviour.
"Issues of this serious nature should not be litigated in Parliament in such a manner. It was wrong. Parliament rightly needs to set standard for others to follow."