Mayors have warned of knock-on effects to other industries and a devastating impact on regional communities if a major fertiliser plant in north-east Queensland is allowed to close, as politicians at three levels of government demanded intervention to ensure that does not happen.

The Queensland government said it had done a thorough analysis of the Phosphate Hill fertiliser plant near Mount Isa that concluded the plant was economically viable, and it expected owner Dyno Nobel to “act accordingly”.