The switch from five commissioners to four for Trans-Tasman Resources (TTR) second seabed mining application gave chairman Alick Shaw a casting vote.
And that has angered Kiwis Against Seabed Mining (KASM), a group which has strenuously opposed the application to mine ironsand off the South Taranaki coast.
The application was to the Environmental Protection Agency and was heard by a panel of four commissioners. Two supported the application and two were against it, leaving Mr Shaw to approve the application on August 10 by using his casting vote.
"The chair ... had an extra vote that pushed the decision over the line. This is concerning," says Cindy Baxter, secretary of KASM.
"If there were any doubts, the legislation directs the decision makers to err on the side of caution."
Exclusive Economic Zone (EEZ) legislation says: "If ... the information available is uncertain or inadequate, the EPA must favour caution and environmental protection."
TTR's first application was heard by five commissioners, which eliminated the possibility of a casting vote. It was rejected in 2014.
An EPA spokeswoman said: "The number of members is usually three to five. The exact number is decided on a case-by-case basis, with reference to the nature and scale of the application."
TTR has been given permission to mine 66 square kilometres of the seabed between 22km and 36km off Patea for 35 years.
But Ms Baxter said the company had failed to present enough new scientific information to the hearing; had failed to carry out marine mammal surveys; had failed to study creatures on the seafloor; and had failed to measure undersea noise which could be a huge issue for marine mammals.
It was this lack of baseline monitoring (finding out about the environment as it is) that saw two of the commissioners oppose the application.
Dissenting commissioners Sharron McGarry and Gerry Te Kapa Coates said the lack of baseline monitoring meant it would be impossible to know what the effects of the mining were. They declined the consent because without background information they couldn't assess how sensitive the environment was.
Because of the lack of background information, TTR must do two years of baseline monitoring before mining can start.
Ms Baxter said it was not TTR but the South Taranaki Reef Life Project and Dr Leigh Torres' blue whale study that provided new scientific information during the consent hearing.
She also said that since August 2016, TTR had claimed to be at least 50 per cent New Zealand owned.
She said on August 9 last year the company moved 48 per cent of its shares from a Netherlands body to a New Zealand one that was ultimately owned by an Auckland law firm. The move, which took New Zealand ownership to just over 50 per cent, was described by Ms Baxter as a "trick" known as "securities lending".
She said the mining proposal was the first of its kind anywhere in the world, and the United Nations' International Seabed Authority was still working on international rules around seabed mining.
The Namibia and Northern Territory governments had imposed moratoriums on seabed mining, and KASM would like an international moratorium.
The Chronicle asked TTR to comment on Ms Baxter's views. The company responded with an email saying it's unable to respond and inquiries have been passed to the project team.