The authority released a consultation paper on the proposal, with submissions due on February 10, 2017. No date has been set for a final decision to be made, but it is expected in the first half of 2017.
The proposal, if it went ahead, will be implemented in 2020.
"This $8.8m increase is a wealth transfer from Northlanders to the shareholders of the big generators, which includes the government, and foreign owners," Mr Peters said.
Ms Collins said she would not intervene as she did not have the power to direct a Crown entity such as the authority.
She said the authority continued to consult on TPM and was open to feedback from stakeholders.
"The authority has shown that it is open and willing to meeting with stakeholders throughout this process in order to discuss concerns and its reasoning.
"It has also demonstrated that, where appropriate, it will amend its proposal in light of feedback," she said.
Authority CEO Carl Hansen said apart from the TPM proposal, Northland power users may get a slice of between $25 million and $35 million in estimated savings if subsidies for generators connected to electricity networks were removed.
However, the authority could not provide the estimated savings for Northland power users.
Transpower would analyse its national grid operations, beginning with the lower South Island, before advising the authority whether the subsidies should remain or be removed.
If Transpower is of the view its generators are helping distribute power in some or all areas, the Avoided Cost of Transmission (ACOT) subsidy will remain.
Under current rules, consumers are subsiding power distributors and over the past eight years, ACOT has increased by 79 per cent nationwide.
A number of Northland groups and individuals, including Northpower and Top Energy, have made submissions on the TPM.