This Four Corners investigation has uncovered gangs of black market workers run by unscrupulous labour hire contractors operating on farms and in factories around the country.

These labour hire contractors prey upon highly vulnerable young foreigners, many with very limited English, who have come to Australia with dreams of working in a fair country.

They're subjected to brutal working hours, degrading living conditions and the massive underpayment of wages. With female workers particularly at risk with women coming forward to make allegations of harassment and assaults.