National Party Leader Judith Collins is challenging the Prime Minister to sack Parliament's Speaker.
Collins sent a letter to Jacinda Ardern on Wednesday, in which she questions her request to reconvene a cross-party working group to decide how to deal with sensitive staff conduct matters, such as sexual assault.
Jacinda Ardern sent a letter to Trevor Mallard last week, asking that the group reconvene after the Speaker rape allegation saga blew up in the House.
When appearing before the House as the Minister Responsible for Parliamentary service, Mallard used Parliamentary privilege to accuse a former staffer - he had previously falsely called a rapist - of sexual assault.
In Collins' letter to Ardern she said as Labour leader, she has shown no indication she will remove Trevor Mallard from the role of Speaker.
"The irony of you, now, using your position as Prime Minister, to request the Speaker, Deputy and Assistants to reconvene their committee simply beggars belief," Collins said.
Collins said it wasn't for the Prime Minister to say the debate fell short of behavioural standards, "that is a matter for the Speaker, in the Chair, not for the Prime Minister to decide."
She urged Ardern to sack Mallard "for the sake of upholding the integrity of Parliament".
A spokesperson for the Prime Minister said the letter she sent to the Speaker "simply reiterated the request for the cross party Parliamentary Code of Conduct Steering Group to be reconvened."
There was nothing in the letter Ardern hadn't already said publicly and all party leaders were copied in, they said.