Senator MILNE (Tasmania—Leader of the Australian Greens) (14:33): Mr President, I ask a supplementary question. I take from the minister's answer that revenue over the forward estimates from this tax are under threat. Will the minister now admit that the government made a mistake in its deal with the multinational mining companies in agreeing to credit unlimited royalties and that the government should have supported the Greens amendment to limit the credit of royalties to those that were in place before 1 July 2011.