The Australian Manufacturing Workers Union (AMWU) confirmed 90 per cent of its members at BHP’s Pilbara port operations had backed the proposal to stop work, with strike action expected to be imminent.

BHP could lose $100 million in revenue a day if two unions vote for work stoppages, unless it can find about 450 replacement staff in Western Australia.

Unionised workers at BHPs operations in Port Hedland could walk off the job as soon as next week after endorsing protected industrial action.