The Electrical Trades Union (ETU) says more than 250 Ergon Energy workers in Queensland broke out in rashes and vomited after wearing new suits, rolled out recently at a cost of about $3.5 million. Ergon Energy is a state-owned corporation.
One man had welts that left his back numb, while others reported blistering and rashes covering their groins, arms and nipples.
Workers also claim the uniforms release a yellow, bubbling substance when ironed that causes nausea and vomiting.
Ergon has sent samples of the workwear for testing but the Electrical Trades Union is demanding a full recall.
While at least 143 workers have lodged health and safety complaints, ETU assistant secretary Peter Simpson said more than 250 workers were affected.
"We only got wind of the problems in August but it looks like a lot of the men were suffering the symptoms in silence," Simpson said.
Lodged complaints don't include members of the workers' families who also have reported symptoms after coming in contact with the uniforms.
Simpson said: "It is a serious issue. We don't know and they aren't telling us what the short and long-term effects of these things are.
"One doctor has advised an Ergon employee that the effects of the chemicals could be cumulative."
An Ergon staff safety directive obtained by The Courier-Mail advised employees last week to continue wearing the new uniforms if they didn't have access to the old variety and had not experienced rash symptoms. If the worker no longer had the old uniform, they were advised to order it and revert to it "as soon as practicably possible".
But Simpson said the response was not sufficient.
"Everyone should have been out of the uniform before last week, no ifs or buts," Simpson stressed.
"They needed to do a mass recall. Ergon has a duty of care to provide a safe workplace."
An Ergon spokesman admitted: "There was not a mass withdrawal of uniforms in the first hit."
He added: "The technology used to make the uniforms flame-retardant is not new or radical. We have used it in good faith that there haven't previously been problems with it.
"Initial test results were inconclusive but tests are continuing."