Opponents of a proposal to mine millions of tonnes of ironsand from the seabed off the Taranaki coast say the hearings process has been biased.
They say the Environmental Protection Agency (EPA) has bent over backwards to help the applicant Trans-Tasman Resources prove its case, at the expense of those opposed to it.
Trans-Tasman Resources has applied for consents to dig up 50 million tonnes of the South Taranaki Bight seabed every year for 35 years, for a net return five million tonnes of iron ore annually.
The company says it will earn about $400 million in export earnings a year, with the government pocketing about $6m in royalties, and create about 300 jobs.
Opponents claim the technology is unproven and the project could do irreparable damage to sensitive marine environments.
Kiwis Against Seabed Mining (KASM) spokesperson Phil McCabe said a last-minute request for Trans-Tasman Resources to provide more information on the sediment plume and noise was unfair on other submitters.
"To call for brand-new information is just not OK, because that information needed to be at the front-end of the process and our view is that this call for new information makes this whole hearing process essentially null and void."
Mr McCabe said the call for new information came on top of an earlier extension to allow the company to get more data, for an application that he said should have been rejected in September last year on the basis of being incomplete.
He feared there were other factors in play.
"It's clear to us that there is downward pressure upon the EPA, being placed upon the EPA, to get this application over the line.
"It's obvious with three ministries MBIE [the Ministry of Business, Innovation and Employment], MPI [the Ministry of Primary Industries] and DOC [the Department of Conservation] all giving it the tick and the go-ahead."
Mr McCabe said KASM would seek a judicial review of the process, a declaratory statement, or an appeal on the basis of a flawed process.
"It is demonstrably clear that the EPA has embarked on an exercise of completing and, in effect, proving the applicant's case. This is an unlawful exercise of power which also significantly prejudices submitters in opposition to the application."
The group was not alone. Fisheries submitters, Ngāti Ruanui and Forest and Bird were also angry, and all wrote to the EPA to say so.
Ngāti Ruanui chief executive Debbie Ngarewa-Packer said when it wanted more time or information the authority put up road blocks, but it had done the complete opposite for Trans-Tasman Resources.
"Our general view which has been emphasised throughout this whole ridiculous process has been if the information wasn't clear in the application at the beginning it shouldn't have been accepted.
"And this behaviour, this need for them to have more information, further validates our concerns."
Ms Ngarewa-Packer said the iwi was also planning a legal challenge and she feared there would be backlash among her people if the application was approved.
"I think they'll be incensed, I think they'll be furious and there's a large degree of being resigned to being ripped off and treated poorly.
"I think that they are absolutely appalled at the disregard they've faced as the little people and there's very much the sense of David versus Goliath."
In its response to the submitters' criticism, the chairman of the authority's decision-making committee, Alick Shaw, said the Exclusive Economic Zone Act imposed an obligation on it to seek information throughout the hearings process and provided wide powers for it to do so.
"The requests for further information are made with due consideration to the obligation to establish a procedure that is appropriate and fair. The DMC [decision-making committee] has always taken steps to ensure that there is a process allowing parties an opportunity to respond, and this will continue to be the case."
The EPA has received more than 14,000 submission on Trans-Tasman Resources' application, the overwhelming majority against the project.
The hearings are now due to end at the end of May, and a decision on whether it is approved is due 20 days later.