UNION workers are threatening to plunge the east coast into a power crisis and leave families struggling to turn their lights on after ramping up strikes across coal mines in Queensland and NSW.

And the Construction, Forestry, Mining and ­Energy Union (CFMEU) along with their comrades in the Maritime Union of Australia are demanding a ludicrous deal that would force Glencore, the operator of the eight mines, to guarantee it won't fire any of its 1400 staff.

The union strikes - which are worst at Oaky North in Queensland - have spread south, starting in May, and could strangle coal supplies within months.

Workers have been on strike at Oaky North since April and have been locked out of the mine since July 20. AGL, operator of the Liddell power plant in the Hunter Valley and the larger Bayswater station nearby, is so alarmed it raised the issue directly with Prime Minister Malcolm Turnbull.

The Daily Telegraph has obtained a briefing note handed to the PM's Office and to Energy Minister Josh Frydenberg on September 6 which says the strikes have "the potential to provide significant interruption to coal suppliers". AGL has also ­requested "support from the federal government as it appears that negotiations have stalled and may subsequently impede coal delivery".

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