Mining company Trans-Tasman Resources is appealing the High Court decision which removed its consent to mine iron sand from the South Taranaki seabed.
The High Court decision was released on August 28, and follows consents granted the previous year by the Environmental Protection Authority (EPA).
The consents were appealed by several groups representing environmental, iwi and fishing interests.
Trans-Tasman Resources (TTR) wants consents to suck up 50 million tonnes a year of iron sand from the seabed 22-36km offshore from Patea, for a period of 35 years.
It would ship 5 million tonnes of iron-rich material to Asia each year, returning the rest of the sand to the seabed.
High Court Justice Peter Churchman said the consents were illegal under exclusive economic zone legislation, because they allowed the discharge of sand particles without any certainty of their effect.
TTR chairman Alan Eggers has asked the Court of Appeal for leave to appeal that decision, rather than going back into a new EPA consenting process. He has asked for an urgent hearing.
The basis for the TTR appeal is that the EPA did follow a legally correct approach in granting the marine discharge, he said.
It included a comprehensive set of conditions designed to protect the marine environment and existing interests, especially those of iwi.
Opponents of seabed mining now have until October 5 to decide whether to cross appeal.
Kiwis Against Seabed Mining (KASM) may cross appeal on points of law that Justice Churchman didn't consider relevant, chairwoman Cindy Baxter said.
If it does, TTR will be able to respond. Even if it doesn't cross appeal, KASM will have a right to be heard in the Appeal Court.
South Taranaki tribe Ngāti Ruanui is also planning to be there. It will uphold Justice Churchman's view that giving the discharge consent on insufficient information was an error of law, chief executive Debbie Ngarewa-Packer said.
Ngāti Ruanui was awarded costs from some of its past spending to appeal the consents, and if TTR loses again it could have to pay more. It would be very foolish for the company to go to the Supreme Court if it loses again, Ngarewa-Packer said.
Other appellants, including neighbouring tribe Ngā Rauru, are all considering their options.