The comments come after 60 supervisors at South32’s Appin coal mine were locked out for taking protected industrial action over a roster change.

The week-long lockout, which began on Monday, followed management’s attempt to “force a new roster onto supervisors”, the Collieries Staff & Officials Association (CSOA)  has said.

The roster required supervisors to work an extra four hours for no additional pay.

The locked-out workers have been temporarily replaced, in some cases, by “very inexperienced people off the street” who were “rushed through training”, the CSOA’s Kylie Rooke said.

Read more: Appin mine supervisors protest ‘dangerous and irresponsible’ decision

Rob Powell, from Horsley, has been in the industry for almost four decades and was a supervisor at Appin. 

The 57-year-old said the supervisors, also known as deputies, were responsible for mine production areas (or districts) – including the “absolutely critical” role of managing gas levels – and the safety of workers.

“You’ve got to learn that mine, it’s as simple as that. You’ve got to learn the layout, its conditions, how it reacts during production,” Mr Powell said.

“It is a very, very gassy mine and that’s a real concern for a lot of the people.”

Mr Powell said the gas produced during the cutting of coal posed a number of risks – including “frictional ignition” when the machinery used struck the roof.

Read more: South32 locks out workers at Appin coal mine

“You’ve got to be aware of your whole district during a production shift; it’s absolutely critical, it’s just so important,” he said. “Sending people in there with minimum experience, it’s not ideal. It’s far from ideal, actually.

Mr Powell said a little problem, if not dealt with promptly and properly, could lead to “big problems” and permanent staff knew “what to look for”.

“If you’ve got contract labour coming in, there’s no ownership for those guys who are the contractors; they might be at Appin one month, then they might go back to Queensland or whatever,” he said.

Mr Powell said the dispute over the extra four hours was “all smoke and mirrors”.

“The bottom line is they want contract labour; they don’t want permanent employees, they don’t want permanent South32 deputies; they want contract mining,” he said.

“It’s happening throughout NSW, throughout Queensland and this is just the tip of the iceberg in the Illawarra,” he said.

An Illawarra Coal spokeswoman told the Mercury this week that South32 had “removed the deputies from site for one week in the interests of the safety and stability of the mine”, which was currently being “safely operated with skilled and qualified alternative labour”.