The Construction, Forestry, Mining and Energy Union (CFMEU) said it intends to step up strike action at six of BHP Billiton Mitsubishi Alliance’s (BMA) coking coal mines in Queensland’s Bowen Basin.

More than 3,500 workers have been involved in rolling stoppages over the last 15 months amid protracted negotiations over a third rostered break for workers on night shifts and more family-friendly rosters.

Unions involving truck drivers, electricians, cleaners and other workers are also opposed to the company’s plans to have supervisors not covered by the Enterprise Agreement, perform health and safety roles.

The CFMEU is planning to hold meetings with members across the Bowen Basin mines, iincluding Goonyella-Riverside, Peak Downs, Saraji, Norwich Park, Gregory-Crinum and Blackwater, to discuss stepping up strike action, despite BHP’s claim that it has lost $2bn due to industrial action and poor weather in March.

CFMEU district president Stephan Smyth told the Australian Associated Press, "This sits squarely on the shoulders of the company and it doesn’t change our plans to escalate industrial action."

The force majeure now means that BHP can’t meet its obligations to its customers, BHP Billiton BMA spokeswoman Fiona Martin told the news agency.