Labour Party MP Darren Hughes, who is being investigated by police, has resigned from Parliament, saying his position has become untenable.
The list MP has been on leave from Parliament after it was revealed on Wednesday that an 18-year-old man had lodged a complaint against him with police.
The complaint relates to an incident at Mr Hughes' Wellington residence early on 2 March and is understood to be of a sexual nature.
On Friday, the 32-year-old released a statement coinciding with a media conference Labour leader Phil Goff gave announcing the decision.
Mr Hughes has again insisted that he has done nothing wrong, but says it has become clear to him that the concept of innocent until proven guilty does not apply in the political arena.
He says his immediate focus is on clearing his name and co-operating with the inquiry. "I have done nothing wrong, and I remain confident that the legal process will have the right outcome."
However, Mr Hughes expects that will continue in the glare of publicity and says he is not prepared to see the Labour Party distracted in the lead-up to the election in November.
Mr Hughes thanked Mr Goff and deputy leader Annette King for their support and expressed his gratitude to the people of Horowhenua and Kapiti.
Labour Party president Andrew Little says Mr Hughes has acted in the best interests of the party in tendering his resignation, but his loss is "very unfortunate".
The next person on Labour's list is former Auckland Central MP Judith Tizard, who lost the seat in the 2008 election.
Ms Tizard says she is shocked by the resignation, but is not ruling out returning to Parliament.
Goff defends handling of matter
Radio New Zealand's political staff say some Labour MPs are privately questioning Phil Goff's handling of the matter, with one saying it was distressing to learn that he knew about the complaint about Mr Hughes for two weeks, but did nothing until it became public.
However, Mr Goff on Friday defended his actions and believes he has full support of his caucus.
"By requiring his resignation at the beginning, I believe I would have been pre-judging that matter.
"But he has made the decision that the pressures that exist, the controversy that's surrounding this case now make it impossible for him to carry out his duties. I agree."
Mr Goff says he has not talked with anyone on the Labour Party list about filling the vacancy.