The miner said yesterday it had instructed lawyers to prepare and file legal proceedings.
The Te Kuha proposal involves consents from both the West Coast Regional Council and Buller District Council, approved four years ago, and a concession sought from the Department of Conservation to cross 12ha of conservation land to access the hillside mine site.
However, four years after Stevenson applied for the concession, it was turned down at the weekend by Conservation Minister Eugenie Sage and Energy and Resources Minister Megan Woods.
The mine would create 58 full-time jobs in an area that has lost hundreds of mining jobs at Stockton, and more than 100 with the closure of the Cape Foulwind cement factory.
The proposed mine site itself is largely not on the conservation estate but mostly on 110ha of the Westport Water Conservation Reserve.
"Stevenson has received legal advice that there are grounds to challenge the ministers' decision declining access by way of a judicial review in the High Court," chief operating officer Anne Brewster said yesterday.
Stevenson has asked the Environment Court to adjourn the separate resource consent hearing until the High Court action has been decided. Forest and Bird is appealing that.
Ms Sage said in making the decision the Te Kuha area was one of the last two areas of intact, elevated Brunner coal-measure ecosystems in the country.
"It is an undisturbed area which is precious and unique and supports complex and diverse habitats for threatened plants and wildlife including great spotted kiwi, land snails and lizards," she said.
Straterra, New Zealand's minerals sector industry organisation, said yesterday the West Coast Regional Council and the Buller District Council had already granted a resource consent under the Resource Management Act.
