Several groups will continue to fight a proposal to mine the South Taranaki seabed in the courts.

Kiwis Against Seabed Mining (KASM), with Greenpeace, has sought leave to cross-appeal the matter in the Court of Appeal.

The Taranaki-Whanganui Conservation Board has done the same.

Both want to set a strong precedent for assessing the impact of seabed mining.

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They are seizing a chance to broaden the grounds on which the mining cannot be consented. KASM wants a second ruling on the way an Environmental Protection Authority (EPA) committee used a casting vote to gain consent in August 2017.

It wants the fact economic costs were not factored in with economic gain to be considered, as well as the way the mining would cross a boundary from the exclusive economic zone into the coastal zone. It wants a judgement on how the precautionary principle should have been applied.

The Conservation Board wants to defend the position of High Court Justice Peter Churchman, who quashed the consent granted by the EPA. It would also like to confirm the quashing on other grounds.

South Taranaki iwi Ngāti Ruanui has also said it will continue to fight the proposal.

The mining company, Trans-Tasman Resources, wants consent to mine iron-sand 22-36km offshore from Pātea. It would send the iron-rich 10 per cent to Asia for processing, returning the rest of the sand to the seabed.

The EPA refused consents for the proposal in 2014, then granted them, after a second hearing, in August 2017.

The matter was appealed to the High Court by a mix of iwi, environmental and fishing interests. Justice Churchman's August 28 decision quashed consent.

It was then appealed to the Appeal Court by Trans-Tasman Resources.

Now that cross-appeals have been sought the matter can be opened wider in the Court of Appeal.