SANTIAGO- U.S.-based Albemarle Corp, the world's largest lithium producer, has accused its top rival, Chilean miner SQM, and local regulators of seeking to keep secret a coveted report about the environmental impact of lithium mining in Chile's Salar de Atacama, according to a filing made by its lawyers.

Chilean regulator Corfo, which oversees lithium mining in the Atacama, in August denied a request from Albemarle ALB.N to review the long-awaited report, according to filings obtained by Reuters under Chile's Transparency Act. In the filings, Corfo told Albemarle it was unable to provide the report because it was still under review and contained confidential business information.

The report, which remains under wraps, aims to stamp out uncertainty over the sustainability of mining activity that has long cast a pall over the sensitive salt flat, home to one-quarter of the world's current output of lithium, but also indigenous communities, protected areas, and endangered flamingos.

Both SQM and Albemarle, the only two lithium miners on the flat, contributed to the report. But whereas SQM's contract with Corfo allows it to review working drafts of studies commissioned by the agency and related to water in the Salar, Albemarle's contract does not include this clause.

SQM SQMB.SN objected to the study's release, the filings show, arguing the data it contained was "sensitive and confidential."

Albemarle blasted Corfo's decision in an August appeal presented to Chile's Council for Transparency and seen by Reuters, calling the study long-overdue, and its contents public. The council resolves disputes related to the country's open records laws.

"Their only goal is to hide information that is, in no way, secret," Albemarle's attorney said in the filing, adding that the study in question was "highly relevant" to understanding the environmental effects of mining on the flat.

It said the only reason the contents might be sensitive was if they "revealed non-compliance or actions that go against regulations" and said SQM's exclusive right to review the study was unfair and put its top competitor in a "position of privilege."

Corfo declined to comment on the dispute.

SQM did not comment directly on Albemarle's accusations when contacted by Reuters. The Chilean miner said in a statement that Corfo had "independently contracted top-level specialists" for the water study. SQM added it had adhered to the terms of its contract with Corfo and provided the agency with all of the information regulators had requested.

The study and the true state of the Salar's water supply has long been an obsession of lithium industry watchers because of the area's huge importance in satisfying soaring global demand for the white metal. Lithium is vital to the batteries that power cellphones and electric vehicles.

Lawmakers, academics, environmentalists, local communities, German carmaker Volkswagen and most recently, a Chilean environmental tribunal, have all emphasized the importance of the study in helping dispel lingering questions on the impact of lithium mining in Chile. 

Corfo said in the filings the revised study will be completed by February 2021. The agency did not say if, or when, the document might be made public.

(Reporting by Dave Sherwood, Editing by Rosalba O'Brien) ((dave.sherwood@thomsonreuters.com; +56 9 9138 1047, +56 2 2370 4224; Reuters Messaging: dave.sherwood.thomsonreuters.com@reuters.net))