The council refuted the claims, arguing it had developed comprehensive plans to address the environmental concerns - which have evolved over recent weeks as a result of discussions with submitters at the inquiry - and had consulted extensively.
Late on Tuesday lawyers for the council, NKII, Te Taiwhenua o Heretaunga and Te Taiwhenua o Tamatea told the board that a meeting the previous day had reached agreement on further amendments to the proposed plan change, new conditions for the water scheme and an expanded plan for offsetting the impact of the project.
A joint memorandum filed with the board said the Maori groups involved considered the proposed changes "positive developments as part of a necessarily longer process" that would need to be considered by the marae and hapu of the Lower Tukituki.
The memorandum said the proposals did not address the full range of issues raised by Maori groups during the hearings, particularly in relation to environmental standards. There had been no agreement reached on water quality and quantity issues or the disputed validity of the so-called TRIM model used to predict the impact of nutrient run-off as a result of the Ruataniwha dam.
The chairman of the regional council, Fenton Wilson, said yesterday discussions between the parties would continue as they fleshed out details, especially around environmental monitoring.
"From the council's point of view it's satisfying that we've got to a better place than we were, say, a couple of weeks ago," he said.
The cost of the new initiatives was not yet clear.
The board is expected to produce a draft decision in early March, which will be open to submissions and followed by a final decision in April. "I'm confident we will get a fair outcome," Mr Wilson said.