The union has lodged a complaint with the building industry monitor, Worksafe, against Perth building firm Hanssen Industries for employing up to 100 non-English-speaking workers from China and the Philipppines.
Managing Director Gerry Hanssen says he's been forced to look offshore because of a shortage of tradesmen in Perth.
But the CFMEU's Kevin Reynolds says Mr Hanssen is employing cheap migrant labour because no Australian will work for the wages he's offering.
"For the same type of hours that these guys are required to work, he's paying about half the rate which any other construction company in Perth would expect to pay, plus none of these blokes speak English.
"They haven't got a clue on our safety provisions. We've lodged a complaint with Worksafe today and they'll be doing investigations on this.
"If it is as we say then they'll end up getting orders on them to do something about it."