Despite being under investigation for assault allegations, Labour's Māori caucus is standing behind its co-chair, Meka Whaitiri.

The side-lined MP is absent from parliament, but Labour's Māori MPs say natural justice should be allowed to take its course.

It's alleged that she shoved one of her staff members during a heated argument. 

But Peeni Henare the Tāmaki Makaurau MP still supports her as the co-chair of Labour's Māori caucus.

"Tā te mea he mea rerekē te take kei mua i tana aroaro, ēngari e haere tonu ana ngā mahi ki roto i tana rohe pōti, anō hoki kei runga i te poari whakahaere o ngā mema Māori."

Prime Minister Jacinda Ardern wouldn't divulge her opinions or give any comments about the issue, but she said that she'll wait for the outcome of the investigation. 

"I'm letting this process run its course I don't want to get into any of the detail around the back in forth or the conversations they've had. I want natural justice to apply here and that means leaving it to ministerial services."

The leader of the opposition Simon Bridges says he doesn't like Ardern's reasoning.

"Frankly if the minister can't give her complete assurances about what's gone on, it seems to me it's pretty clear what a Helen Clark or a John Key would have done - she would be fired."

The outcome of the investigation is expected to come out in two or three weeks.