The dispute began in October last year when the Construction, Forestry, Mining and Energy Union accused Xstrata of breaching OECD guidelines on workplace relations at its mines in the Hunter and Queensland.

It laid specific complaints about redundancies at Xstrata's United mine near Singleton and accused the company of "poor labour practices" and anti-union behaviour at most of its sites, including another Hunter mine, Glendell.

The complaint was lodged with the Australian National Contact Point, an arm of the Foreign Investment Review Board.

The union also accused Xstrata of "anti-competitive conduct" with its biggest shareholder, Swiss company Glencore.

Xstrata denied the union's claims and accused it in return of anti-Semitism over website postings about certain Xstrata executives.

Union national president Tony Maher said Xstrata had "thumbed its nose" at international corporate guidelines by refusing to work with the federal government body responsible for hearing the first round of OECD complaints.

The review board contact point said last week it had been "unable to fulfil its key role" of bringing the parties together through conciliation. It was disappointed Xstrata had refused to meet directly with the union over the matter.

Xstrata spokesman James Rickards said Xstrata had not taken part in conciliation because it had not contravened OECD guidelines and had no case to answer.

He said Xstrata had responded fully to the contact point and believed "the union's actions indicate they are not prepared to engage with us in good faith".

He was unsure what would happen next but it was possible the matter would go to the OECD.

He said the union's xstratafacts.com website had "frequently misrepresented Xstrata's actions and included content that ranged from offensive comments to racial vilification and threats of violence".