The Green Party says Dr Elizabeth Kerekere has resigned from their party effective immediately after a heated Zoom call with party members.
She will sit as an independent MP until the next election, when she will retire.
Dr Kerekere has been under investigation over her behaviour after she was apparently caught calling fellow Green MP Chlöe Swarbrick a "crybaby" in a message sent to the wrong group chat.
Since then a number of allegations have surfaced about her behaviour towards other Green Party MPs, staff and members.
The party launched a probe into Dr Kerekere, led by conducted by musterer (whip) Jan Logie and chief of staff Robin Campbell.
"As we have stated on numerous occasions, we committed to an internal process to look into these matters that was fair to everyone involved," the party's co-leaders Marama Davidson and James Shaw said in a statement on Friday night.
"Before that process could conclude, Dr Kerekere resigned as a Green Party MP and Green Party member."
They added they don't intend to use the 'waka jumping' Act to kick her out of Parliament.
Earlier on Friday night, Dr Kerekere lashed out at Davidson and Shaw in a Zoom meeting with Green Party members, saying they had made it difficult for her to continue working in the party.
Sources say she criticised the time it was taking to complete the investigation, seeing it as an attempt to sabotage votes for her for the Greens' final list rankings.
On the draft list, Dr Kerekere, a first-term MP, was ranked fourth; one place below Swarbrick, but above some senior MPs.
Last week, Dr Kerekere's supporters attempted to delay voting on the Greens' final list rankings until the investigation had finished. The attempt failed.
According to RNZ, during the Friday night Zoom call, Dr Kerekere denied any allegations of bullying. She also reportedly blamed another Green MP for leaking her messages and said she was under attack because she stands up against racism.
However Shaw and Davidson took issue with her remarks.
"We have been informed that Dr Kerekere made a number of statements whilst addressing party members tonight, that we consider to be untrue. We do not intend to address these tonight, but will do so over the coming days," they said.
"We wish Dr Kerekere all the best for her future."