Newshub has obtained emails that show Labour was sent details six months ago of sexual assault allegations against a party staffer. 

The party continues to deny it knew the claims against the man included sexual assault, but on Tuesday the Prime Minister said the party President Nigel Haworth has to go if it's proven he mishandled the allegations. 

Newshub has been forwarded an email sent by a complainant to one the members of the Labour Party investigating panel on the day of her interview. 

She wanted to be able to read off a timeline and testimony. She asked if someone could print the document before her interview which was taking place an hour later. 

A document "to print sexual assault experience" was attached. 

Prime Minister Jacinda Ardern was shown the document on Tuesday morning. 

She told Newshub, "You'll understand why we will want to take away this and look at it directly."

Labour agrees the email was sent but claims there were no documents attached. The complainant says all three members of the investigating panel were given a printed copy. 

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National's deputy leader Paula Bennett says she has "absolutely no doubt at all" that the panel knew. 

"I think it is a cover-up. I think that it's got to such a point that they know that their own heads will roll, that they're actually almost doing the lying in unison, from what I can see."

The attached testimony included details of the alleged sexual assault, and how she felt in the aftermath of the incident. 

• "I would find myself crumbling down at the sight of him, I couldn't sleep, [and] I couldn't eat."
• "Always thought of the Labour Party like a family, but the family just doesn't want to talk about sexual assault or bullying."
• "MPs who used to protect us, you - and then would turn away."

Newshub revealed in August Finance Minister Grant Robertson was aware of the investigation and some complaints, but he's refusing to say how much he knew. 

"I am not going to comment any further than what I have on that because I will be undermining the privacy," he told Newshub. 

Jobs are now on the line. 

The Prime Minister said she will expect Haworth's resignation if he's found to have done something wrong. 

Haworth said he is "not resigning" but will "look into my situation as the process develops". 

National leader Simon Bridges suggested the blame's falling on the wrong person. 

"Whose employee is this person? It's not Nigel Haworth's - it's Jacinda Ardern's," he said. 

It's one of the few facts not being disputed.