The Crown is being accused of giving iwi carbon credits and failing to prevent their value from collapsing.
Some tribes were given the units as part of their Treaty settlements, but over the years the price of the credits has dived.
Chris Karamea Insley, who advises the iwi leadership group on climate change issues, says the group blames the Government for the price fall and would consider taking a contemporary claim to the Waitangi Tribunal for the loss of $600 million.
He says any claim would assert that iwi reasonably expected the credits to retain their value, and the Crown did not take steps to preserve their value.
Mr Karamea Insley says iwi negotiated their carbon credits in good faith.
