Private prosecutor Graham McCready plans to take Fonterra to court because of its move to make creditors wait 90 days for bill payment.
He said that went against the normal course of trading in New Zealand, and breached the solvency test under the Companies Act.
A company satisfies the solvency test if it is able to pay its debts as they fall due in the normal course of business.
Mr McCready, who has filed private prosecutions against many politicians in the past, said it was an offence for directors to continue to trade if the test was not met.
He said he would file his case in the Auckland District Court against two Fonterra directors once he had statements from creditors confirming that Fonterra would only pay after 90 days and not the usual 20.