The body, which looks into the way the Polish state operates and how it spends public funds, says the company has spent more than $5.2B in three years on the underperforming Sierra Gorda mine.
Tambao, one of the world’s largest manganese mines, has been halted since 2015 after Burkina Faso's new government ordered the company to stop production.
Mining stopped on March 8, when members of the Asociación Obrera Minera Argentina (AOMA) downed tools, and processing activities have now also ceased following the exhaustion of surface stockpiles.