His concerns were echoed by ASX-listed Alumina Limited which, along with Alcoa owns the majority of western Victoria's Portland aluminium smelter, and warned that long-term outages could be damaging. Last week Coca-Cola Amatil boss Alison Watkins likened the situation to one the company would face in developing countries like Papua New Guinea while Bluescope has also raised concerns. Loading Costa's major production facility in Victoria is a mushroom farm on Melbourne's northern fringe which employs about 600 staff and produces about 20 per cent of the mushrooms consumed in Australia. "We put in five huge standby generators, permanently wired-in. It cost us $2.3 million, two-and-a-half years ago...and we've done a similar thing in our glasshouses and other operations across the country," he said. "Now we shouldn't have to do that. We've had to step in and guarantee reliability. The cost is the other issue, but if you're a producer or a manufacturer, the one thing you've got to do is ensure you can stay in production."

Alumina chief executive Mike Ferraro said the company was confident it could handle short-term outages but extended blackouts could take a heavy toll on the smelter, as was the case in 2016 when a loss of power caused pot lines to freeze, requiring millions of dollars in remedial works. Mr Ferraro said the looming risk of blackouts in Victoria raised a "broader question" about the state of the east-coast energy market. How have we allowed the eastern seaboard to get to the position it's in today where there are risks of power shortage. Alumina CEO Mike Ferraro "How have we allowed the eastern seaboard to get to the position it's in today where there are risks of power shortage [and] there are very high energy costs which impact businesses such as ourselves?" he said. "We are really looking for strong committed federal and state energy policies to be enunciated and put in place."

The AEMO's warnings have reignited political divisions over energy and what policies are required to bring stability to the network. Loading Federal Energy Minister Angus Taylor on Sunday said the Coalition government was working hard to ensure reliability and affordability, including underwriting and investing in dispatchable energy capacity such as Snowy Hydro 2.0 and introducing new rules forcing retailers to meet the needs of customers with enough dispatchable, round-the-clock power. "We've done a number of things to deal with what is a serious problem in reliability and affordability, particularly when the sun has gone down and the wind isn't blowing on tough days in summer," he said. But he said one of the biggest problems for energy reliability was the speed at which the Victorian government was seeking to introduce renewable energy into market – a renewables target of 50 per cent by 2030 – without the baseload capacity to support it.