Forrest described the Gillard Government proposed Minerals Resource Rent Tax as "economic vandalism" and a "mad dog's breakfast" that would drive up foreign resource ownership. He stated he would challenge it in the High Court as being unconstitutional, as it discriminates against states, and fails to appropriately capture big producers BHP Billiton and Rio Tinto. WA premier Colin Barnett has stated the state government would back constitutional action, admitting the tax had been suggested to him as a "sovereign risk". He was highly critical of the government's expenditure of $38M on an advertising campaign, that was not approved using the usual processes, as it had to "counter mining industry 'spin' about the resources super profits tax".