By David Fickling Of DOW JONES NEWSWIRES SYDNEY (Dow Jones)--The prospect of Australia's Green party taking control of the country's Senate in August 21 elections creates fresh uncertainty for mining companies in relation to the government's proposed mining tax, executives and lobbyists said Thursday. But the miners refused to say whether they would restart advertising against the tax, a move that was seen as escalating the debate over a previous version of the tax in May which 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 and Exploration Companies. "We're certainly not ruling it out." He said a campaign could be restarted as soon as this weekend, but 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), said that the Green party's support for a tougher version of the tax went against their 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 were 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 will control 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 government on its design, BHP Billiton Ltd. (BHP.AU), Rio Tinto Ltd. (RIO.AU), 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 refused 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 22:45 ET (02:45 GMT)