The Australian federal government is facing a legal challenge to its mining tax on the eve of its introduction. Fortescue Metals announced in Perth on Friday that it has formally begun proceedings in the High Court.
The Minerals Resource Rent Tax is due to come into effect on 1 July.
The company says it has received legal advice showing the legislation breaches the constitution.
Chief executive Nev Power says the tax discriminates against the states and restricts a state's ability to encourage mining.
Fortescue rejects the suggestion it is trying to avoid paying taxes that will share the benefits of the mining boom.
The mining tax is to be levied at 30% on the super profits of iron ore and coal companies.