The Australian Senate is expected to vote on the tax at about 9pm AEDT.

Given the political make-up of the Senate, almost nobody expects the MRRT legislation to be knocked back.

Association of Mining and Exploration Companies chief executive officer Simon Bennison said the investment market was already feeling extremely nervous in view of uncertain global economic times.

“Many emerging producers and explorers are already experiencing problems raising capital for projects in Australia and are looking to transfer their work to overseas jurisdictions that are also resource rich,” Bennison said.

“The introduction of this anti-competitive legislation in Australia will only further push investment capital offshore and change our reputation as a safe place in which to invest.

“This could have lasting consequences.”

Bennison said he was amazed a tax favouring large multinational businesses and discriminating against smaller businesses could be passed through Parliament.

“The tax is simply unfair to smaller emerging miners and is so complex that the administrative and compliance burden on industry and government will be extreme.

“Expert independent modelling undertaken by the University of Western Australia confirmed small and emerging miners will be paying a higher effective tax rate than the larger mature miners.

“The differential could be as much as 4 per cent.”

Bennison said the tax rate in the UWA modelling included income tax, royalties and the MRRT.

There could be worse to come though.

Bennison said the Australian Greens would push to have the MRRT amended to remove the deductibility of state-raised royalties against the tax.