Thousands of jobs will be cut and Lake Macquarie two mines will be closed unless Origin Energy renews its coal supply contract for Eraring Power Station, three Hunter mining unions say.
However, Origin rejected claims it had abandoned contracts with the Myuna and Mandalong mines to provide coal to the power plant and said negotiations were ongoing.
Origin's contract with Centennial Coal, who owns both mines, expires in June.
Negotiations have been ongoing since the start of the year. Union delegates said the energy giant was dragging its feet and accused it of "abandoned its own mining community".
Myuna was created purely to supply Eraring, with coal transported straight to the power plant via conveyor belt. There is no other way to export the coal and without the Origin contract, the mine would be forced to close.
The nearby Mandalong mine contributes around half its coal to the power station, and significant job losses will be incurred without a new Eraring contract.
Collieries' Staff and Officials Association lead organiser Belinda Giblin said that Origin Energy's refusal to renew its contract with Centennial made a mockery of the company's commitment to the principles of a "just transition".
"For over 40 years, staff at the Myuna and Mandalong mines have successfully supplied the Eraring power station. As a reward for their loyalty and hard work, Origin Energy is taking away their jobs and dumping their communities on the scrap heap," Ms Giblin said.
Origin says it remained in discussion with Centennial Coal and was hopeful that an agreement could be reached that was "consistent with the terms at which we have secured other coal supply agreements".
"Locking in higher priced coal when there are cheaper options available from other domestic sources risks putting upwards pressure on wholesale electricity prices for NSW customers," an Origin spokesperson said.
The future of Eraring Power Station remains up in the air. The power plant is due to be closed in September 2025, however a decision to keep the facility open for longer is expected to be made soon, due to the slower than expected transition to renewables.
Regardless of what happens, Ms Giblin said Eraring would need coal for at least another year.
"It doesn't need to be a 10-year contract, but there does need to be assurances coal is sourced from Myuna and Mandalong first and foremost, that's what's best for the local community," said.
The Electrical Trades Union and Australian Manufacturing Workers Union join CSOA's call for government intervention to ensure the coal supply contracts were renewed.
Independent Lake Macquarie MP Greg Piper backed the miners and called on Origin to return to the negotiation table.
"We keep talking about energy transitions and soft landings, but the miners and their families, they don't get much of a say," Mr Piper said.
"It's a terrible situation. If we do see an untidy shut down, there will be significant job losses in a short period of time and that will be felt right throughout the community."
