Greens leader Christine Milne has announced plans to set up a Senate inquiry into the failure of the mining tax to raise any significant revenue.

The tax raised $126 million in its first six months, well short of the full-year forecast of $2 billion.Senator Milne told the National Press Club today she plans to move to establish the inquiry when the Senate resumes next week.She says an inquiry will get to the bottom of the tax's flaws and what needs to be done to fix it."I'm confident we'll get the numbers to be able to have this inquiry into how we got to the situation we have, where the mining giants are not paying their way," she said."Rio Tinto's celebrating not paying any tax and meanwhile the pockets of single parents have been raided to fill up the shortfall.