Community and environment groups are calling for an inquiry into flood damage at the Yallourn power station that put Victoria's power supply at risk.
A state energy emergency was declared in June after cracks appeared in the Morwell River diversion that runs through the coal mine during severe floods.
The diversion previously collapsed after heavy rainfall in 2012, which flooded the mine and shut down the Yallourn power station for weeks.
The station supplies up to 22 per cent of Victoria's electricity and eight per cent of Australia's. It is set to close in mid-2028.
The groups, led by Environmental Justice Australia and Environment Victoria, have written to Premier Daniel Andrews calling for an independent investigation into the damage to the Morwell River diversion.
Environment Victoria Campaigns Manager Nicholas Aberle the government had failed to answer serious questions over the incident, including whether EnergyAustralia properly rebuilt and maintained the diversion following its collapse in 2012.
"The MRD is on private land, but the damage affects the Morwell River which supplies freshwater to the internationally recognised Gippsland Lakes downstream. That makes this a matter of serious public interest," he said in a statement.
On Tuesday, the Australian Energy Market Operator warned further flooding at the mine was the biggest risk to the nation's power supply this summer.
