UK-based Darley Energy has complained to the European Commission at Poland's decision to not award it the potash mining concession, near the Baltic coastal town of Puck.
In 2012, Darley bid for the concession, which is expected to be valued at nearly €1.5bn ($1.65bn).
The company said that there were no other bidders at that time and according to Polish law it should have been granted access to the deposit by May 2013.
As the bidding process was extended, Polish mining company KGHM joined and successfully bid for the concession.
According to Darley Energy, Poland's decision to grant the permit to KGHM was 'illegal public aid'.
Reuters reported the company as saying in a statement that the government had granted the permit 'without conducting the necessary procedures of an open, transparent, competitive and non-discriminatory concession process."
In 2014, Darley submitted an appeal to Poland's Environment Ministry, which oversaw the bidding process.
In December, the company's appeal was rejected.
Poland's Environment Ministry said KGHM had the strongest bid, so won the concession.