Labour leader Chris Hipkins says former Green Party MP Darleen Tana should resign from Parliament and has no mandate to continue as an independent.
Tana resigned from the party after an investigation into allegations of worker exploitation at her husband's business.
The Greens called a caucus meeting unanimously demanding that she resign from Parliament.
"The reality is, she was elected as a Green member of Parliament, she's resigned from the Green Party and so she should resign from Parliament," Hipkins told RNZ's Morning Report programme today.
He said he did not want to pass any judgement on the issues around migrant exploitation involving Tana.
"She doesn't have a mandate to be an independent MP, she was elected as a Green MP. She no longer is, so she should go.
"She's not entitled to be an independent MP. Nobody voted for her to be an independent MP - they voted for the Greens and she became an MP because of that."
Tana's campaign for the Tāmaki Makaurau seat was unsuccessful, but she entered Parliament at 13th on the list after last year's general election.
Hipkins said the Greens would be well within their rights to invoke waka jumping legislation, designed to prevent MPs from ditching their party during a parliamentary term that could see Tana evicted from Parliament.
"I think it would be an appropriate course of action for them to take, should they decide to do that."
The Greens have been strongly opposed to that legislation despite voting for it in 2018 because they felt they were required to under their coalition agreement with Labour and New Zealand First.
Hipkins said he believed the Greens had been opposed to the legislation based on the idea an MP could be forced out for disagreeing with the party, but that was not the case here.
"The case here is that someone has been allegedly conducting themselves in a way that makes them unfit to be an MP and I think that makes it different."
Tana claims that "natural justice" has not been followed during the investigation, but Hipkins disagreed.
"They've put the allegations to her personally, they've given her a chance to respond to them and so on.
"The investigation went on for months, I don't think you can say that they haven't made an effort to hear all sides of the story."
Hipkins was asked why Labour did not invoke the waka jumping rule for former MP Meka Whatiri, who quit Labour and stood unsuccessfully for Te Pāti Māori in last year's election.
"Had she resigned two years before the election, I would have," Hipkins replied.
"The reality is, I didn't want to complicate things by having a vacancy in the Ikaroa-Rāwhiti electorate literally within a couple of months of the general election."
