A Maori Trust claims the re-designed $10 bank note, due to be released next month, has used their pattern without permission.
The tukutuku panelling features on the background of the note and was taken from the Te Hau ki Turanga meeting house in Te Papa Museum.
But the Rongowhakaata Trust, which legally owns the whare, says it wasn't consulted and has called in the lawyers.
Spokesperson Robyn Rauna says the Reserve Bank didn't ask for permission.
"We think it's an honour to have people want to use our things, but first – just basic courtesy – ask."
She wants an apology and for the Reserve Bank to admit its mistake.
But the Reserve Bank's adamant it has the legal right to use the design.
It says the New Zealand $10 banknote has used this image since Series 6 was introduced in 1993.
"The Bank understands it is a generic East Coast pattern [and on that basis may be hard to distinguish from similar patterns," it says in a statement.
"This particular image was supplied to us by an appropriate representative of Te Hau ki Turanga wharenui. The Bank had no reason to consult with any other party."
Along with the $10 bill, an upgraded $5 bill will enter general circulation from next month.
The remaining $20, $50 and $100 bills will be introduced in April next year.