A lawyer specialising in Treaty of Waitangi claims says Maori tribe Tuwharetoa has an obligation to its people to seek a fee from Mighty River Power for using Lake Taupo.
The central North Island iwi is pushing for the electricity generator to pay several millions of dollars a year for using the tribe's property.
Tuwharetoa owns the lakebed and says it has the right to charge commercial users under its Deed of Settlement with the Crown.
The issue has been flagged as a potential investment risk in Mighty River's share offer document.
Janet Mason from the Pacific Law firm says it is about time that the iwi asserted its rights.
"I don't think they're bold at all. I think that this is something that is expected of the leadership. I think they need to make these moves on behalf of their people."
Earlier this year, Tuwharetoa imposed a fee for Iron Man using the lake in the swimming leg of the triathlon.
An energy consultant says asking for money over water will continue to be a festering issue if Maori water rights aren't made clear.
East Harbour Energy director Brian Cox was an expert witness for the Maori Council in its recent water rights tribunal hearing and says if the issue is not resolved, it will continue to go on to hold back any development of water.
Mr Cox says any use of water is affected by what proprietary rights parties have.