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.
Developing of one of the world's biggest untapped copper and gold deposits is currently stalled by a multi-billion dollar legal wrangle with foreign mining firms.
The project now contains 423 million indicated tonnes grading 0.41 gram gold per tonne, 0.22% copper, 4.6 grams silver and 41 parts per million molybdenum.