Australian federal government faces renewed hurdles on passing its mining tax in parliament, with key independent members of parliament (MPs) on Monday threatening to withdraw support unless the government implants stricter rules for coal seam gas proposals on farm land. Labor has yet to win enough crossbench support to have its 30 percent Mineral Resources Rent Tax (MRRT) pass parliament. As key Independent Andrew Wilkie is yet to come to a decision on the tax, Tony Windsor, an independent MP on Monday also insisted his support for the tax will come with conditions attached. Windsor wants up to 400 million U.S. dollars a year set aside from the tax revenue to fund bio-regional assessments, which would scientifically measure the impact of coal seam gas and other mining practices on farm land. He also wants greater Commonwealth powers over mining projects approvals, now the domain of states and territories. \"It would look at all the spatial landscape issues from landform, soil productivity, vegetation management, threatened species, other environmental issues, including groundwater, and surface water, and how the cumulative effects of some of these industries would impact downstream on others who are nowhere near the mining or gas activity,\" he told reporters in Canberra. He is also demanding the Commonwealth legislate powers give itself final approval of mining projects, effectively overriding the states. Another key independent, Rob Oakeshott, is making similar demands. However, it seems unlikely Windsor\'s demands will find support from the government, as Prime Minister Julia Gillard said land use is not a Commonwealth matter. \"Predominantly this is a state government matter, to manage land use and resources, but of course we will discuss Tony Windsor \'s concerns with him,\" Gillard said. On another front, the Australian Greens are insisting gold miners be subject to the new tax, but said they will support the tax even if the amendments are defeated. Labor minority government requires an additional four non-Labor votes to secure 75 votes against Coalition\'s 74 votes to pass the bills in parliament. So far, only the Greens has thrown certain support over the tax. The MRRT, which will apply only to iron ore and coal, is due to begin on July 1, 2012, and is budgeted to make about 11.4 billion U.S. dollars in its first three years.