The Minerals Resource Rent Tax (MRRT) was forecast to raise $2 billion in its first year of operation, but after six months only $126 million has been raised.
Ms Milne says she will be urging the federal government to fix the mining tax after it failed to raise the promised billions of dollars.
“Fix the mining tax – the money is there to be had,” Senator Milne told reporters on Monday.
She will attend a committee hearing on Monday afternoon, which follows hearings in Perth and Canberra.
“Witness after witness makes it perfectly clear the government did a deal with the mining companies which essentially gave the government a political win and the mining companies a massive profit win,” she said.
Representatives from BHP Billiton, Rio Tinto and Xstrata will appear before the committee on Monday.
Prime Minister Julia Gillard struck a deal on the tax with the three mining giants in 2010.