Tauranga iwi Ngāi Te Rangi is threatening to blockade the harbour to protest Port of Tauranga dredging and expansion plans.
The consent process for those plans is held up in court and the port says that is the right forum to deal with issues.
The iwi's chief executive, Paora Stanley, has written to the port's board giving notice it will take "direct action" to reinforce its opposition to a consent sought by the port that includes dredging 1.8 million cubic metres of sand from the harbour seabed.
Stanley told the Bay of Plenty Times the action could extend to an on-water protest where a flotilla of boats would attempt to block ships from entering the port - a form of protest it used in 2017 during a dispute with Hauraki iwi.
He said he had informed the port and other authorities, and should the iwi take this blockade action, it would give 48 hours' notice.
Stanley said direct action was about trying to draw attention to the key issue of concern for the iwi, which was what he viewed as the "level of degradation" of the harbour since the port's original 2011 dredging consent.
The port has applied for consent for a 385m wharf extension and 1.8ha land reclamation at Sulphur Point, as well as wharf extensions of 530m north, and 388m south, of the tanker berth and a 2.9ha reclamation on its Mount Maunganui wharves.
The company says the associated extension to the shipping channel covers 14.4ha and involves dredging up to 1.8 million cubic metres of the sea floor.
If the application is successful, the port estimates the project will take three years, cost $68.5 million and create 368 jobs in the construction phase, and more than 81 permanent jobs after construction.
Consent for the expansion was supposed to be the subject of a 10-day Environment Court hearing in Tauranga starting on Monday but was put off until 2023.
On July 5, Stanley wrote to the port chairman and board members saying the iwi will begin taking "direct action", including looking into a Waitangi Tribunal case.
In the strongly-worded letter, he said: "As governors of the Port of Tauranga and by default having control over the quality of our harbour through your decisions, I would like to petition you, as a board to put our moana first.
"Our people who traverse the moana daily (and in my case weekly) over the years, have noted the declining nature of the harbour. This has been significant since your original consent in 2011. We were of the view when the consent was granted that the pristine nature of our moana would not be affected but that had not been achieved.
"The good cop bad cop, blame individuals and groups strategy that you are initiating has ended in the Environment Court, I'm tired of the egomaniacs determining our environmental destiny, this is playground negotiations which will now be met with direct action."
Stanley said "humility and environmentally considered" business strategies were not terms the iwi believed were associated with the port's business.
In the iwi's view: "Traffic congestion, ease of influence with your big budgets and sheer size, acting like an ill-considered juggernaut are what is associated with you now."
He wrote that bringing money into the local economy was important, but having that as "an excuse" to act in a way he perceived as "environmentally, culturally and community bereft" was not.
In Ngāi Te Rangi's view, the iwi was "deliberately excluded" from the usual process of having a say on the 2021 resource consent application for the "enormous" sand dredging.
"We have seen what [impact] a fraction of that has had on silt and the destruction of pipi beds that many people including our own have valued for many, many decades. This is and will always be wrong."
Stanley said as chief executive he had reassigned $1.1m a year for three years to assist in the rebuilding of the harbour - "more than 10 per cent" of the iwi's internal budgets.
"To bring attention to the traffic congestion your business contributes to, we intend to show you how congestion on YOUR roads and entrances will impact you. We will find a way to show you what happens when you can no longer get juggernaut access to enter the harbour at will.
"To get you to understand the importance of land and the moana to us, we will begin
the process of investigating the implications of the Waitangi Tribunal case against you and your business supporters.
"Business and environment can come together in a sustainable way and whilst you pout with your perceived power it will NOT occur - please advise now how you would like this lesson delivered to you ..."
Asked about the letter, Port of Tauranga chief executive Leonard Sampson said: "The Environment Court is the best forum to debate these issues and outside of the court we will not make any comment about the contents of this letter."
He said it was "extremely disappointing and frustrating" to have the hearing adjourned, especially after it had taken quite a lengthy process to get to that point.
"We will continue to persevere but with New Zealand's supply chain already under severe strain, the further delay in getting a hearing will prolong the congestion impacts.
"We really hope the Environment Court can expedite matters by finding some hearing time this year."
Priority One CEO Nigel Tutt said such a lengthy delay to hear the consent application for a project of national and regional significance was "hugely concerning".
"This hearing had already been delayed a couple of years and it's frustrating to see further court hearing delays for a major critical infrastructure project such as this."
Tutt said the delay meant the port's capacity constraints were only going to get more demanding, as would supply chain issues for businesses over the next couple of years.
"It's frustrating and very concerning not just for the port but for Aotearoa," he said.
Tauranga Business Chamber chief executive Matt Cowley said the port's extension project was of "national significance" and the delay in the time-sensitive decision was "disappointing".
He said this was especially true given the economy was hamstrung by supply chain issues.
"There have been plenty of studies and strategies that reinforce the importance of the Golden Triangle [Auckland, Hamilton, Tauranga] logistics network to New Zealand's overall economy.
"The Port of Tauranga plays a critical role as the country's exporting gateway to the world.
"Approval processes like this should look at the overall net benefit for New Zealand's wellbeing. Delays ... only reinforce the need to reform the Resource Management Act," Cowley said.
The industry faces challenges but hopes to bring newcomers and veterans together.