The Maori Council says it intends to launch a judicial challenge against the Government's decision to partially privatise Mighty River Power.
On Monday, the Government confirmed it will proceed with the partial sale of the state-owned company between March and June 2013, but will not include a special shareholding for Maori in recognition of rights over fresh water.
Finance Minister Bill English says the Government maintains its belief that no-one owns the water and Maori rights and interests can be recognised in other ways.
Maori Council co-chairperson Donna Hall said on Tuesday it has spoken to representatives of the Maori King, various hapu and iwi regarding that decision.
"The view from all of these gatherings is that there is no choice now but to seek review of the Government's decisions through the courts.
"There are expected to be some fairly important meetings over Thursday and once these are completed there will be a decision made, and of course, there'll need to be some fairly rapid action from there."
The council says it still needs to speak to other groups in the central North Island on Thursday which have not had a chance to make their views heard.
However, it says it has already agreed in principle to file court papers against the sale before the end of this week.
A lawyer for the council, Felix Geiringer, says any such court action would challenge the partial sale's legality under the Treaty of Waitangi.
Mr Geiringer says costs of legal action are an issue for the council, which he says is not so abundantly funded that it can make such a decision lightly.
"The problem is that the Government has quite deliberately been boxing them into a corner. It's really forcing them to court."
Bill English says it is preferable that any court proceedings begin now, so they can be dealt with before the planned float next year. He says legal aid will be an option if Maori decide to go to go to court, as anyone who does so can apply for legal aid.
Mr English says it became clear to the Government in its consultation hui in September that most iwi do not regard the council as speaking for them.
Ngai Tahu not revealing stance
The chairman of Ngai Tahu, Mark Solomon, is not saying whether the tribe will will support the Maori Council in its fight.
But Mr Solomon has hinted at differences with the Maori Council by saying he has faith in the Land and Water Forum.
The forum was set up by the Government and aims to sort out water rights with Maori, farmers, business people, local government and others.
The Maori Party will vote against the partial sale of Mighty River Power but co-leader Pita Sharples is making clear the party will not walk away from its support agreement with National.
Dr Sharples told Radio New Zealand's Morning Report programme he has had many discussions with Maori on staying with National. He says the message from many people is for the party to stick with its support agreement so it remains at the centre of Government and continues to make a difference.
The New Zealand First leader Winston Peters says the Government's decision to proceed with the partial sale is stupid and bloody-minded as economists and the Treasury agree the sale isn't justified.