A $US12 BILLION foray into Canadian potash has been tipped as the most likely of BHP Billiton's ''mega'' growth projects to face a delay or reduced investment.

Coal and coal seam gas (CSG) miners may be banned from southeast Queensland's Scenic Rim district under a Liberal National Party (LNP) government.

Global miner BHP Billiton Ltd is looking to build a new rail line between some of its inland Australian coal mines and the coast in a move that could threaten dominant coal haulage firm QR National Ltd, a newspaper said.

Amid pressure from the Greens for the government to make the mining tax even harsher, the Prime Minister today urged Tony Abbott to force the mining industry to share the benefits of the boom. “Is this really a time for anybody to come to this parliament and say the MRRT should be opposed ... in view of the profitability of mines and the pressures we know are on other sections of the economy because of the high Aussie dollar?” she said. “That is a strategy for wrecking.”