Taranaki Māori tribes are refusing to step aside for a company's plans to vacuum 50 million tonnes off the seabed for a mining project, only to dump most of the unwanted sediment back into shallow waters south of New Plymouth a year later.

The proposal has Trans-Tasman Resources looking to extract iron, vanadium and titanium from a South Taranaki seabed for 35 years, with the Australian company currently going through a new and also highly controversial fast-track process to gain consent in the New Zealand Supreme Court.

Trans-Tasman Resources says it will discharge 45 tonnes of leftover seabed in an environmentally safe process after mining off the coast of the small town of Pātea.

But all eight local Taranaki iwi unanimously oppose the actions add their support to the local mana whenua, who have thwarted plans – so far – through court challenges.

Ngā Iwi o Taranaki – the collective iwi group representing the most western region on the North Island – voiced their concern on seabed mining in a recent statement

"Our iwi stand alongside our southern iwi to support them and to amplify their concerns about seabed mining in their takiwā (territory)," Ngā Iwi o Taranaki mana pouwhakahaere (authority manager) Wharehoka Wano said.

"We encourage all iwi to support our South Taranaki whānau in their deep opposition to Trans-Tasman Resources and seabed mining."

Opponents are seeking an urgent Waitangi Tribunal injunction to halt the processing of the company's application under the Fast-track Approvals Act.

Trans-Tasman Resources managing director Alan Eggers claimed the company held a number of extensive interactions with affected southern iwi.

The company applied to the Environmental Protection Authority for permission to mine for minerals in South Taranaki Bight around a decade ago.

"We're very disappointed at the lack of engagement that (the iwi) have given us," Mr Eggers said.

"They haven't engaged; they've refused to engage with us. We would love to engage with them and, let me say this, we are going to be working with South Taranaki iwi when we get our consent, whether they like want us or not.

"We're going to want (the local iwi) on board and were going to want them to actually do a lot of this marine monitoring and research."

Te Tai Hauaūru MP Debbie Ngarewa-Packer said the company's claim of engagement and offer of jobs was absurd given the consistent rejection from mana whenua Iwi authority.

The Pāti Māori co-leader has led the Ngāti Ruanui, a neighbouring iwi and the wider community of opponents, in the fight against the miners.

"Taranaki iwi and community haven't fought and won in every court for the last 12 years for him to say, 'get over it'," Ms Ngarewa-Packer said.

"He's in a rush to please his shareholders and we care about our environment and community."

The stand from Trans-Tasman Resources, a subsidiary of ASX-listed mining company Manuka Resources, came as a shock to the Protect Our Moana Parihaka uri (community descendant) spokesperson Tihikura Hohaia.

"He certainly hasn't come to consult with any of us grassroots whanau, hapū that are keeping our home fires burning on our marae... not at all, I can tell you that right now," Mr Hohaia said.

Mr Hohaia has not heard any factors in Trans-Tasman Resources proposal which would help gauge support from Iwi people.

Mr Eggers recently told the Taranaki Regional Council it could generate export revenues of $1 billion a year, making the mining company the country's 11th or 12th largest exporter.

The project would create approximately 1320 jobs and generate $190 million in government royalties and taxes per year, Mr Eggers said.

The project, according to the New Zealand Institute of Economic Research, would set to benefit the region with 305 new jobs directly linked to the miner, 1125 Taranaki-related jobs indirectly in areas of logistics and supplies, in addition to $NZ250 million Taranaki operational spend each year, $NZ55 million in royalties to the Taranaki iwi community, $NZ36 million in corporate tax and $NZ855 million in foreign exchange earnings.

"I don't believe it – it mustn't go ahead," Mr Hohaia said.

"If it goes ahead, it's going to condemn our already impoverished, trampled uri to generations of protest."

Opponents also have environmental concerns about the plume created by dredging the sea floor, but a dismissive Mr Eggers argued water near the site would be no more turbid than during a stormy day.

Mr Hohaia said the Southern Taranaki iwi is standing against the project on principle "with dignity".

"(The proposal) felt very violent against a backdrop of a cultural upbringing in an area of land loss and so the pure focus on economics ... seemed totally bereft of any wairua, of any spirit at all," he said.

Taranaki councillor and lawyer, Amanda Clinton-Gohdes, who successfully led the motion at the New Plymouth District Council to oppose seabed mining off the Taranaki coast, is leading the cultural arguments against an offshore mine at Taranaki Regional Council.

This action expands the regional response of the opposition to the project – joined a further two coastal district councils – alongside local iwi and firm support from the wider community that says it will be impacted.

Ms Clinton-Gohdes is also concerned that the proposal competes to the detriment of both the recreational and commercial users of the marine area, including for the fishing, wind energy and tourism industries.

"Proposed seabed mining operation poses significant environmental risks to marine biodiversity and culturally significant areas, while offering uncertain long-term economic benefit," she said.