Gujarat NRE failed to pay mine workers their wages this week and cannot guarantee when they will be paid.
The Association of Professional Engineers, Scientists and Managers Australia (APESMA), which looks after nearly 100 workers at Gujarat, said staff should have been paid on Wednesday afternoon and had been given no guarantee their wages would be paid next week.
Gujarat said yesterday that it was "experiencing difficult times" because of a mining downturn, lower coal prices and a high Australian dollar, but hoped to make the payments "as soon as possible".
It expected operations and cash flow to stabilise after the acceptance of the Jindal Steel and Power share offer at the general meeting on October 16.
However, APESMA collieries staff division director Catherine Bolger said workers had been told the money "may" come in next week but "maybe not".
Members were also owed several months of superannuation as well as a $13,000 coal bonus from last year, she said.
"This is incredibly disappointing for staff who have shown remarkable commitment to the company over many months," she said.
"Workers have the right to be paid on time - Gujarat is not living up to their responsibility to pay workers; they are being unfair in the extreme.
"It's simple - Gujarat needs to pay its workers, on time, every week."
Staff from both the Russell Vale and Wongawilli mines are expected to attend meetings today to discuss the situation.
Ms Bolger called on Gujarat management to be transparent about their finances.
"We want to work with the company - this current situation is completely unsatisfactory.
"Staff have been working with the company while it has been trying to trade out of this situation but we've now asked for more details about their financial state."
Gujarat apologised yesterday and asked the union and the workers "to be understanding and work with the company to help them overcome these hard times".
Executive chairman Arun Jagatramka said the company hoped to pay staff as soon as possible.
"[We] want to keep the delay to an absolute minimum," he said.
"As we hear daily, Australia is experiencing a mining downturn, the drop in coal price and a high Australian dollar are all major contributors.
"Gujarat is also experiencing these difficult times but is working to maintain its workforce."