Jacinda Ardern has been accused of a cover-up by suspended Labour MP Gaurav Sharma in an explosive interview likely to cause more pain for the first-term parliamentarian.
Dr Sharma now faces party expulsion next week, with the prime minister's office confirming the caucus would re-visit his partyroom membership at its next meeting.
The renegade Hamilton West MP has been privately feuding with his own party for the past 18 months, and over the last week has gone public with claims of a bullying culture in Ms Ardern's government.
He was suspended from the Labour caucus on Tuesday, with Ms Ardern saying she would not tolerate attacks on her colleagues.
But rather than rein it in, Dr Sharma has gone nuclear, giving a long interview with Newshub where he accused Ms Ardern and her office of deception.
"There is something very big going on here and there is a cover-up," he said.
"This is the prime minister's office trying to cover something, this is the prime minister trying to cover something. And I'm saying this is not just about bullying. There is a lot more to here."
Dr Sharma plans to continue his attacks in other media engagements on Friday.
His central issue appears to be a hiring freeze placed on his office after several members of his staff quit within months of working under him.
For this, he blames former party whip Kieran McAnulty, who he accuses of brutish behaviour and "degrading me in front of colleagues".
But in days of missives, including a Facebook post that stretched to 2634 words, Dr Sharma is yet to produce concrete evidence of the bullying, denied by Mr McAnulty and Ms Ardern.
When suspending the 38-year-old, Ms Ardern suggested he was still upset at the staffing issue.
"We identified - because staff raised it - issues with his management within his office, and interventions were made," Ms Ardern said.
"That's very different from being able to substantiate that you have been bullied."
Dr Sharma has refused to take the PM's calls and says he won't take part in a mediation process outlined by the party, labelling it a "kangaroo court".
Labour MPs met on Monday night without Dr Sharma to discuss the matter, and then held a formal caucus meeting on Tuesday to sanction him.
Learning of the secret Monday gathering, Dr Sharma cut communications with the party, and refused to attend on Tuesday.
"I was genuinely hurt by that," he said.
On Newshub, he produced evidence in the form of a message from another Labour MP which told him the suspension was "predetermined" and it would be "brutal".
Given Ms Ardern told journalists on Tuesday it would not be predetermined, Dr Sharma said Ms Ardern misled the public.
He wants an independent investigation, which Ms Ardern has ruled out.
A spokeswoman for the PM said caucus - due to meet next on Tuesday - would revisit the issue.
"On Tuesday the Caucus suspended Gaurav on the basis of repeated breaches of trust. This latest example of releasing and misrepresenting conversations with his colleague's (sic) reinforces that decision," the spokeswoman said.
"We anticipated Gaurav would continue to re-litigating matters in this way.
"He has still not responded to our communications about entering into mediation, instead using the media to make his points."
