The Maori Council says a claim it is making for control of fresh water, if successful, could lead to consumers having to pay for it.
The Council has instructed Wellington lawyer Donna Hall to file papers with the Waitangi Tribunal saying that Maori owned all freshwater resources before European settlement and they want them back.
The Council says, as an alternative to ownership, it would want a substantial shareholding in the Crown's electricity-generating companies that are for partial sale but would not give a number for what would be acceptable
A spokesperson for the Council, Manu Paul, says if Maori do win control of water, its use could incur a charge.
But Mr Paul says there all this would depend on extensive debate among Maori on the best course of action.
The Waitangi Tribunal has recommendatory powers only.
Debate over legal position
Ms Hall, the lawyer who will be handling the Maori Council case, says indigenous rights to water are well established in international law.
She says the legal position is that indigenous people can own what they own by their own law, not English law.
"This is the international indigenous position", she says.
But a public law specialist and former Act MP Stephen Franks says the case has little legal merit.
He says, in the case of most of the big rivers, the only iwi with some sort of entitlement to claim have already signed comprehensive treaty settlements and those expressly exclude further claims to water.