Labour Māori caucus co-chairman Willie Jackson has refused to condemn his colleague Meka Whaitiri but fellow Labour MP Peeni Henare says there are other Māori MPs who could step up as a minister.

Jackson said Whaitiri remained the co-chairwoman of Labour's Māori caucus, despite being stood down as a minister by Prime Minister Jacinda Ardern.

Ardern said she had accepted Whaitiri's offer to stand aside while an investigation is carried out into a staffing matter by Ministerial Services.

It has been reported Whaitiri was involved in an alleged altercation that became physical with a new staff member.

Jackson, the Employment Minister, told Newshub Nation it was appropriate for Whaitiri to remain co-chairwoman of the Māori caucus.

"In this country we go through certain processes, and she has to go through a process. She's still a Member of Parliament," Jackson said.

Whaitiri is the MP for the Māori electorate of Ikaroa-Rāwhiti, which stretches down the east coast of the North Island.

Jackson denied there were different standards for the Māori caucus.

"What we believe in is justice, and I won't be commenting on the process. But she is still the MP for Ikaroa-Rāwhiti. She is still the co-chair, along with myself, for the Māori caucus. And I think all New Zealanders would agree there has got to be an investigation and a process to go through before we try to shut Meka Whaitiri down."

But Peeni Henare told Te Kāea it offered an opportunity for others in the Māori caucus.

"We have a pool of options in our party. For example, Willow-Jean Prime and Kiritapu Allan, who would make excellent ministers. There's plenty who could do the job and this could be an opportunity for them."

The Māori caucus would meet this week, Henare said.

Meanwhile, serial litigant Graham McCready has filed a formal complaint of assault with police relating to Whaitiri.

In documents emailed to media and police, McCready told police if it didn't investigate then he would take a private prosecution "against the Hon Meka Whaitiri without further delay or notice".

McCready's complaint stated: "The alleged offender became engaged with the alleged victim and subsequently pushed the alleged victim."

The basis of McCready's knowledge appears to be a media report attached to the complaint. He claims the assault happened on a specific date at Parliament but provides no material to support the claim.

A police spokesperson confirmed a complaint had been received and was being considered.