Shares in Energy Resources of Australia have plunged more than 20 per cent after Kakadu's traditional owners rejected the miner's plans to expand development of the Ranger uranium mine.
The community's opposition could mean the Rio Tinto-owned miner has to write down the value of its assets.
Shares in ERA fell 25 per cent to a low of 29 cents on Thursday, and were down eight cents at 30.5 cents at the session's close.
The company has authority for mining and processing activities at the Ranger mine, which lies inside Kakadu National Park, until January 2021, and is allowed access to carry out rehabilitation activities until January 2016.
ERA had hoped to extend the dates so it could develop the Ranger 3 Deeps underground deposit.
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However the Gundjeihmi Aboriginal Corporation, which acts for the Mirarr traditional owners, has formally told ERA that they are against any extension.
ERA said it will continue to process ore from existing stockpiles and will undertake a review of its business in light of the decision.
The company lost half its board earlier this year after it put on hold feasibility studies to mine the Ranger 3 Deeps deposit because of a sluggish uranium market.
ERA has said it would need to extend its operations beyond the present authority, which expires in 2021, for the project to proceed.
Rio Tinto has completely withdrawn its support for ERA's plans to mine the Ranger 3 Deeps underground deposit.
The Gundjeihmi Aboriginal Corporation has previously demanded ERA produce a comprehensive plan for the clean-up of the site, which must be reintegrated into the surrounding national park by 2026.
