Winston Peters says King Tuheitia is being used by adviser Tukoroirangi Morgan to get involved in domestic party politics and he should remain neutral.
"It is disappointing the Maori King has been used in such a sad way," the New Zealand First leader said.
"There is no way his predecessor, the Maori Queen, would ever have done that."
She knew there were different views within the Kingitanga movement and she had to stay above the political ruck.
King Tuheitia criticised Labour and New Zealand First during an unscripted part of his speech at Turangawaewae coronation celebrations at the weekend.
"It really hurt me when the leader of the Labour Party says 'I'll never work with that Maori Party.' I'm not voting for them anymore," Tuheitia said.
Referring to Peters, King Tuheitia said: "New Zealand First, I don't know about those fellas.
"He might be a Maori but he doesn't act like one. But he's got the right name. You know, New Zealand First - we were here first."
Morgan, a former New Zealand First MP, was last month elected president of the Maori Party. He has since been in talks with Hone Harawira's Mana Movement, a breakaway from the Maori Party, with a view to greater co-operation in the lead-up to next year's election.
Morgan is also a close adviser to King Tuheitia and is his representative on Te Ara Taura, the executive body of Waikato Tainui.
Peters said it was clear the comments made by the King had come through Morgan."Tuku Morgan's track record is not a great one.
"Anyone who had the idea that Tuku's new position in the Maori Party is going to help them just found out how bad the appointment was."Peters said that a matter of weeks ago, Morgan had been talking about the need for Maori and Mana to come together."Now we see this latest tactic using the Maori King as desperation."
King Tuheitia has been head of the Kingiitanga movement for the past 10 years, since the death of his mother, Dame Te Atairangikaahu, who held her position for 40 years.
Tuheitia's cousin Nanaia Mahuta has been a Labour MP since 1996, the same year Morgan was elected MP for Te Tai Hauauru.
He then defected with Tau Henare to break away from New Zealand First and form Mauri Pacific.
King Tuheitia has spent some time in hospital with diabetes-related illness.
Mahuta has been mentioned as a potential successor to him.