Outgoing National MP Nick Smith will get around $87,000 a year in superannuation after he leaves Parliament next week.
The MP announced his shock retirement on Monday after reportedly being told an investigation into a "verbal altercation" was going to be made public on Tuesday.
Dr Smith was allegedly recorded losing his temper and swearing at a "young male staffer" in July last year.
In a statement on Monday, Dr Smith acknowledged a confidential inquiry and its details had been leaked to the media for release on Tuesday, and that he regretted the incident.
"I apologised at the time and I apologise again today. I have decided the best course of action for the parties involved, the National Party, my family and myself is to retire now."
But no details of the investigation have been reported since.
Announcing his shock resignation earlier this week, Dr Smith said he had decided to retire after losing his Nelson seat at the 2020 election, but that investigation had prompted him to leave sooner.
The MP, who first entered Parliament in October 1990, and has been in Parliament ever since as the longest consecutively-serving MP.
Dr Smith is entitled to a "gold-plated" superannuation scheme, according to NZ Herald, and will receive about $87,000 a year for the rest of his life.
This scheme closed to newcomers in 1992, but MPs already in the scheme were able to stay in it.
The median income in New Zealand is about $53,000.
National MP Simon Bridges admitted "there's a whole lot I don't agree with the guy on", but he hopes Smith gives a valedictory speech.
"I hope he gives a valedictory," Bridges told The AM Show on Friday.
"He's had 30 years. I've had massive barnies with Nick over the years, there's a whole lot I don't agree with the guy on, but he's made a massive contribution."