''Would the government have been worse off in the past six months with the original resource super profits tax? Yes. That's a big fat yes,'' said Chris Richardson, a former Treasury economist now at Deloitte Access.

The tax was revised after Mr Rudd lost the prime ministership in a cabinet room negotiation between the heads of the three big mining companies, the Prime Minister, Julia Gillard, the Treasurer, Mr Swan, and the Resources Minister, Martin Ferguson.

''People are screaming that the revised tax is a disaster because it has hardly raised any money. But they would have been screaming more if we had the original tax - it would have cost the government money,'' Mr Richardson said. ''Much of the bad press about the revised tax has been overdone. Yes, it was a hurried compromise, but any super profits tax would be struggling to make money at the moment because the miners aren't making super profits.''

Mr Richardson is quick to point out that the unconditional refund of state royalties wasn't a design fault of the original tax, it was a design feature. The original tax was intended to make things easier for miners in bad times and to grab more of their cream when times turned good. It was announced at a time when they had plenty of cream. In May 2010, the iron ore price was $US160 a tonne. By September last year it had fallen to $US86 a tonne.

''It wasn't just that prices collapsed, it was that the dollar held up as well,'' Mr Richardson says. ''Miners were hit both ways. But since then, prices have climbed back. We are about to enter a phase where the original tax probably would have raised the government more money than the redesigned one. I am not quite sure that we are there yet, but we are getting there.''