Extreme heat, flash floods and airborne diseases could all strike down Australian workers in huge numbers if climate change is not factored into workplace protections, a top union official warns.

Trillions of dollars and millions of workdays will also be lost in a climate-impacted future if safety laws do not keep pace with the warming planet, a report says.

A coalition of firefighters, nurses, teachers and union officials gathered in Parliament House on Tuesday calling for the federal government to acknowledge the impacts of climate change on workers across the country.

Climate-change harms have never been mentioned at joint meetings of workplace health and safety ministers, Australian Council of Trade Unions president Michele O'Neil said.

"We've got a hole in the middle of our work h

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