BHP Billiton has been accused of using "strong-arm tactics" in locking out striking mining supervisors at its Appin mine for the second time in two weeks.
The industrial action is part of a long-running pay dispute between the company and the mine supervisors, represented by the Association of Professional Engineers, Scientists and Managers Australia.
The association's chief executive, Chris Walton, said BHP had announced the lockout after the mine supervisors notified the company of plans to undertake a series of four-hour stopwork meetings in shifts tomorrow and Monday.
"This second lockout is a tactic to intimidate workers, rather than working constructively to resolve a pay dispute," Mr Walton said.
"These strong-arm tactics do not help anyone. In fact, locking out workers just makes it harder to reach an agreement."
The chief executive of BHP subsidiary Illawarra Coal, Troy McDonald, said the company had issued workers taking a four-hour stoppage with notices not to attend work for the rest of their shift.
"Consistent with the company's previous response to part-shift work stoppages orchestrated by the union, we are taking this step to minimise the disruption to the mine's operations and to be able to plan with certainty," he said.
"We need to be able to plan our work and work to that plan for the interests of the broader workforce and to ensure the safety of our people.
"Mining supervisors represent less than 6 per cent of the total workforce, we can't allow a small group of employees to affect our ability to run the mine efficiently."