The ministers Hekia Parata and Pita Sharples have been accused of turning a blind eye to allegations of mis-spending within the Kohanga Reo National Trust.
An Ernst & Young review has found the trust didn't misuse public funds, but didn't look into the financial dealings of its commercial arm, Te Pataka Ohanga.
Education Minister Hekia Parata says that's because the commercial arm isn't publicly funded.
The Taxpayers' Union says that's irrelevant, and has labelled the process a whitewash.
Its executive director Jordan Williams says the key allegation that public money, meant for teaching kids, was used for dresses, fuel and cash withdrawals, was ignored.
He says the Maori Affairs Minister Pita Sharples and Education Minister Hekia Parata have chosen to turn a blind eye to what are serious allegations.
The Serious Fraud Office is now investigating what Ms Parata has described as further 'unsubstantiated allegations of mis-spending' by the commercial arm of the Kohanga Reo Trust Board.
The Department of Internal Affairs also confirmed on Wednesday that its charities services division is investigating the Kohanga Reo National Trust.