A complainant in the Labour sexual assault case has told Newshub they're shocked that a member of the investigating panel who thinks they're lying has effectively taken over as acting Party president.

It follows a litany of failures by the party, including the deputy Labour leader Kelvin Davis referring to the complainants' allegations as "rumours".

Because Nigel Haworth failed complainants in the Labour investigation he was forced to resign as Labour Party president on Wednesday.

Prime Minister Jacinda Ardern, Labour leader, said at the present point in time, the senior vice president holds the role until a new president is elected.

The senior vice president is Tracey McLellan, one of three panellists who investigated allegations against a Labour staffer.

"The holding of that role is a temporary one," the Prime Minister said.

A complainant told Newshub the news is shocking.

"I'm incredibly shocked. I don't feel comfortable at all [or] know how they're meant to facilitate an independent appeal when the party representative is someone who believes we were lying."

They said they feel let down by the party at every level.

The Prime Minister maintains that Monday was the first time she saw "details that a complainant had stated that they had been sexually assaulted".

But Newshub made it clear in reporting and to the Prime Minister's office five weeks ago that a first-hand sexual assault allegation was made to Labour.

And on Wednesday, a complainant told Newshub Finance Minister Grant Robertson was told about the sexual assault allegation.

Robertson told Newshub on Thursday the people involved "need their voices to be heard through the appropriate forum".

But he said he would "not get into any specifics" about whether he knew about sexual assault allegations against a Labour staffer.

And now another minister is caught up in the mess.

Kelvin Davis responded to a speech by National's deputy leader Paula Bennett on Wednesday about the allegations.

A parliamentary translation of what he said is: "Now she stands to disagree with our actions and the work we have done, all based on rumour."

He said the word 'kōhimuhimu' could have meant 'rumours' or 'allegations'.

Davis told Newshub he would not be lectured by a non-Māori speaker on the Māori language.

But there was tautoko from one of Parliament's most fluent te reo speakers.

"Kōhimuhimu means to whisper and gossip," New Zealand First MP and Regional Economic Minister Shane Jones said.

Bennett said it was "disrespectful [of Davis] not taking into consideration the victims and their perspective and trauma in all of this".

It comes as the man at the centre of the allegations announced his resignation from Parliament on Thursday.

The accused says he's enjoyed his time working in Parliament but "made the very difficult decision to resign because of the stress of the situation" and he did not wish to "distract from the work of the Government".

He says he "adamantly refutes" the serious allegations made against him and is cooperating fully with the QC inquiry having been assured the process will be fair to all parties.

Two complainants told Newshub his statement makes them feel sick.

Newshub.