Rio Tinto is facing a Federal Court showdown with the CFMEU following allegations that non-union members were given tens of thousands more in redundancy payouts.
AAP reports the Construction, Forestry, Mining and Energy Union claims non-union workers at the closed Blair Athol mine in QLD received more generous payments than their unionised co-workers .
The union has filed a claim in the Federal Court arguing the different redundancy packages discriminated against union workers and were therefore in breach of the Fair Work Act.
Rio Tinto claims its redundancy package is fair, but if it loses the court battle a ruling could have wider ramifications for the mining sector.
The company claims employees had a choice to work under a collective agreement or individual contract, and redundancy payments were made in accordance with the terms in each worker's contract.
AAP reports the CFMEU claims when 70 workers were laid off from Blair Athol the redundancy package for non-union workers was based on their entire salary, including compulsory overtime and bonuses.
They were also given an extra three months pay as part of the package.
At the same time unionised workers were given redundancy packages based on their base salary only, according to the CFMEU.
The union has previously made allegations of pay anomalies within a number of mining companies, with BHP Billiton also criticised for its pay structures.