More details are emerging as to why Meka Whaitiri has been side-lined from ministerial duties.

The Ikaroa-Rāwhiti MP stepped aside pending an investigation into a 'staffing matter'.

However, it's been reported Whaitiri is accused of shoving a staff member during a heated argument.     

Former Labour Minister John Tamihere says the investigation needs to be referred to a higher authority. 

"It won't be a ministerial investigation that undercovers the truth of that - it'll be a police inquiry because that's an allegation of assault."

But Prime Minister Jacinda Ardern is standing firm on her decision. 

"She offered up to stand aside whilst this investigation takes place. 

"That is the right thing to do and once we have the report completed, then I will make a decision on how to deal with it."

Māori National MP Tutehoronuku Korako supports National leader Simon Bridges call for the outcome of the investigation to be made public.

"The public absolutely needs to know because these are serious allegations, but let's wait and see what the result of that investigation is, but absolutely."

The political career of Meka Whaitiri hangs in the balance.