The campaign against setting up to 200 tidal turbine power generators in Kaipara Harbour shifts next month to the Helensville electorate of Prime Minister John Key, whose government has granted resource consent.
Conservation Minister Kate Wilkinson has approved the $600 million Crest Energy plan on the recommendation of the Environment Court, which set conditions for a staged installation and environmental monitoring.
It is the first large-scale commercial plan to harness tidal flow in New Zealand, and took four years to get through the resource consent process.
But the organisation representing Ngati Whatua hapu, Te Uri-o Hau Settlement Trust, is carrying on its opposition on environmental and cultural grounds.
It is gaining support from a wide range of residents, including Kaipara Mayor Neil Tiller.
After a meeting of more than 300 people at the Dargaville Town Hall, further gatherings are planned.
A hui will be held at Te Hana on April 11 and another the next day at the Helensville War Memorial Hall - in the heart of Mr Key's electorate.
"There is so much opposition to the Crest proposal that the Prime Minister better get back to Helensville for it," said trust spokesman Mikaera Miru.
"People feel passionate there is no way they are going to put the turbines in the harbour.
"It will be further degraded when we are trying to restore its health."
Main concerns were effects on snapper stocks and the survival of the rare Maui's dolphin.
The hapu is understood to have spent about $300,000 fighting the project through its Environs subsidiary.
The minister's approval is for two years of environmental monitoring and evaluation, starting with three turbines.
A publicly notified review is supposed to be held after each stage of installation.
Mr Tiller said the project was "one big experiment".
This was borne out by the consent conditions seeking the development to be halted and turbines ordered to be removed if significant environmental effects are found.
He said upcoming meetings would ensure an organised response and submissions to the review and the next stage when turbines increased from three to 17.