Yancoal is set to cut 50 jobs from its Abel underground coal mine near Newcastle.
A company spokesman said a downturn in the coal market had led the company to review its operations.
CFMEU district president Peter Jordan said talks with the company revealed it had lost $21 million so far this year at Abel mine and expected this number to double.
He said 28 production jobs, 11 tradespeople and nine mine deputies will be cut, Newcastle Herald reported.
The CFMEU will meet with Yancoal today to discuss the changes and Jordan said the union had concerns for workers who will have to work at the company’s Austar coal mine, which has been operating at reduced production levels since two fatalities in April.
Resuming full production at Austar requires state government approval.
Yancoal own six coal mines in NSW and three in Queensland, with a combined workforce of 350.