Labour MP Ginny Andersen is facing a complaint to the party that she bullied a teenage volunteer several times over three years.
RNZ has seen the complaint.
In it, the complainant said their teenage daughter - who had volunteered for Andersen alongside their son - had felt brought down by the MP on multiple occasions, but the worst was on election night this year.
Andersen had yelled at both, the complaint said, claiming they did not do enough volunteering in the election and making them feel that was the reason she lost the Hutt South seat.
The complaint said Andersen had told them: "Maybe you should have done some more doorknocking".
Other examples raised included her daughter being told she was "useless" by the MP over a mixup in 2020, yelling at her over the phone for deciding to attend a family trip instead of volunteering, and brushing aside complaints about bullying by others when this was brought to her attention.
"I think having an MP that represents a party that talks about kindness and having her treat my daughter like this is unacceptable and I want to see some action and the party to take action on this issue."
Andersen has refused to be interviewed, referring RNZ instead to a statement.
"I'm aware a complaint has been made about comments I've made in the past," Andersen said in the statement.
"I'm really sorry if my comments caused hurt. I'm committed to fully engage in the Labour Party process to resolve the matter."
Labour's general secretary Rob Salmond confirmed the party had received the complaint but would not be saying more.
"We can confirm we've received a complaint from a member regarding comments made to them by Ginny Andersen. Complaints and the process to investigate them are confidential, so we can't say anything more at this time."
Andersen has contested the Hutt South seat for Labour since 2017. The seat was won by National's Chris Bishop in that election with 47.88 percent of votes to Andersen's 44.15 percent, but she entered Parliament on Labour's list.
She won the seat off him in the 2020 "red wave" with 50 percent of the votes to Bishop's 41.6 percent, but lost it again in 2023 with 41.28 percent to Bishop's 44.36 percent.
She was elevated to Cabinet in February after Chris Hipkins took over the leadership - with the Seniors, Small Business and Digital Economy and Communications portfolios.
She later took on the high-profile Police portfolio after Stuart Nash's resignation from Cabinet.
In July, she also took over the Justice portfolio from Kiri Allan who had resigned after a car crash in Wellington over which she was charged with careless use of a motor vehicle and refusing to accompany a police officer.
Allan, who did not contest the election, pleaded not guilty in September.