Tribes are accusing the Government of providing the United Nations with false information about the New Zealand environment.
The iwi leadership group says the UN is not being given the whole story about deforestation and the level of commitment to reducing emissions.
The group's adviser, Chris Karamea Insley, made the claims to a monitoring team from the UN Framework Convention on Climate Change committee, which has been visiting Wellington.
He says land is being deforested at an increasing rate and foresters are leaving the Emissions Trading Scheme.
Mr Insley says both of those factors are counter to the objectives of the scheme. He also told the visitors that iwi have lost money through the collapse in the value of carbon credits.