By David Fickling Of DOW JONES NEWSWIRES SYDNEY (Dow Jones)--The prospect of the Australian Greens party holding the balance of power in the Senate after Aug. 21 elections is creating fresh uncertainty for mining companies in relation to the government's proposed mining tax, executives and lobbyists said Thursday. But the miners aren't saying whether they will restart advertising against the tax, which had escalated the debate over a previous version of the tax and ultimately precipitated the overthrow of former prime minister Kevin Rudd. "We're still assessing the future of the campaign," said Simon Bennison, chief executive of the Association of Mining & Exploration Companies. "We're certainly not ruling it out." He said a campaign could be restarted as soon as this weekend, but it may have to wait longer and would depend on the views of AMEC members. Andrew Forrest--chief executive of Fortescue Metals Group Ltd. (FMG.AU), who was at the forefront of the fight against the former Resource Profits Super Tax-- said the Greens' support for a tougher version of the tax went against the party's own agenda to encourage development for indigenous Australians. Greens leader Senator Bob Brown "understands that welfare as a long-term solution in fact exacerbates severely the underprivilege of (indigenous welfare) recipients", Forrest said. "The only long-term solution to get Aboriginal people into the mainstream of Australia is training and employment", and mining companies are best-placed to provide that, he said. Senator Brown said Wednesday his party wanted "a better return from the big miners". Polling suggests that the Greens, which currently have five senators, will hold the balance of power in Australia's Senate after the election, allowing them to block or modify the watered-down version of the mining tax hammered out by new prime minister Julia Gillard. Forrest described the revised proposals as a "retrograde tax" that was "specifically suited to the purposes" of three big mining companies which consulted with the government on its design: BHP Billiton Ltd. (BHP), Rio Tinto Ltd. (RTP) and Xstrata PLC (XTA.LN). That process was "designed to hose down the evident anger of those three multinationals, and not to benefit the Australian people", he said. Fortescue would "favorably consider" any request for funds in the event of a fresh AMEC advertising campaign, but Forrest declined to explicitly back the stance of opposition Liberal-National Coalition leader Tony Abbott, who has called for the tax plans to be cancelled altogether. -By David Fickling, Dow Jones Newswires; +61 2 8272 4689; [email protected] (END) Dow Jones Newswires July 21, 2010 23:33 ET (03:33 GMT)