"In Ngai Tahu's view those rights and interests were not affected by the privatisation of Contact Energy in 1999.
"Nor does Ngai Tahu consider that its rights and interests will be affected by the proposed sale of shares in Mixed Ownership Model companies."
The affidavit further undermines the Maori Council's case by saying Ngai Tahu believed it was premature to resort to either the Waitangi Tribunal or the courts to deal with the issue.
Mr Jones said the affidavit "splits Maoridom over the vexed issue of water rights.
"People are just shaking their heads in bewilderment at what possible upside there could be for the Ngai Tahu leadership to deliberately split Maoridom and to bend over this far for the National Government.
"What possible gain is there by opposing the other iwi? Better just let it be tested in court and if it's a hollow, empty argument then Maori will know where they stand."
Mr Jones, who last week on Maori Television's Native Affairs accused Ngai Tahu chairman Mark Solomon of treachery for not supporting a united iwi approach, said yesterday that the affidavit "does not diminish the accuracy of what I said".
Veteran Maori rights advocate Mike Smith, who had seen the affidavit, said he was suspicious of Ngai Tahu's motives.
"They potentially weaken what could be a strong, unified national Maori position which I think needs to be developed in regard to these matters."
He said Ngai Tahu's stance was unfortunate.
"It's been the North Island tribes, particularly the ones in the north, that have kept the Treaty issues alive through their activism in the last 30 years or so. I haven't been aware Ngai Tahu has led that challenge but they've been happy to ride that train all the way to the station."
Mr Solomon wasn't available for comment yesterday but a spokeswoman said Ngai Tahu's runanga had "consistently stated it is not taking a position on the partial privatisation of any of the SOEs which are under consideration, and that includes Mighty River Power".