Many (many) years ago when I first joined the workforce I remember some businesses wanted me to start work on a "trial" which was unpaid before making a decision about if they wanted to hire me. Even though I felt uneasy about it at the time, it was quite prevalent so perhaps it was legal back then. This was, after all, back in the dark ages.
Unfortunately it seems that some people believe this is still a valid way of getting cheap labour, and they even dress it up with a sexy title of "Intern", but the fact remains that if you asked to do "productive" work that doesn't form part of your studies, then it is quite possible that Company is breaking the law.
The Federal Circuit Court has just imposed a $272,850 penalty against a media company to send it a “serious message” not to disguise employment relationships as unpaid internships.(you can read more on the Fair Work website here)
So when is unpaid work ok?
According to Fair Work, there are limited circumstances such as when you are doing an internship as part of a "structured learning program". These generally form part of degrees offered by Universities. However, if you are filling the role of an employee then you need to be paid accordingly. The Fair Work Ombudsman has a few resources at www.fairwork.gov.au/unpaidwork to try and assist people.
The bottom line is that if you, or someone you know, is asked to work on an unpaid trial or internship which doesn't form part of a learning program through a school (e.g. work experience) or University, then you should do some more digging, and call the Fairwork info line if you are unsure on 13 13 94.