Peabody Energy flagged that this Queensland open cut coal mine was its highest-cost operation almost a month ago and said its output would be reduced by 1.5 million tonnes per annum to 1Mtpa.

While Peabody did not disclose the targeted job cuts, reports at the time indicated that 300 to 350 workers would consequently face the axe.

Construction, Forestry, Mining, and Energy Union district president Steve Pierce has since told the ABC on Friday that more than 100 Thiess contractors received text messages of their redundancies with work ceasing this Friday.

"We're absolutely disgusted,” Pierce reportedly said.

“We haven't seen such morally bereft behaviour since John Howard lost power and WorkChoices went with him.”

A Thiess spokesman reportedly said crews were told the progress of the redundancy program would be communicated by phone.

But he also said using SMS to sack people was a mistake and Thiess had apologised.

The spokesman reportedly said other retrenched staff would be notified in person.