Some workers are being paid just $4 an hour in the unregulated 'black' job market, write Ben Schneiders and Royce Millar in this exclusive report.
Temporary foreign workers in their hundreds of thousands are being illegally exploited and underpaid in "black jobs" in food courts, cafes, factories, building sites, farms, hairdressers and retail across Australia.
A joint investigation by Fairfax Media and Monash University* has confirmed the suspicion of the incoming chairman of 7-Eleven stores, Michael Smith, that underpayments in his company are the tip of a larger iceberg. 
A survey of more than 1000 foreign-language job advertisements reveals a systemic problem more widespread than previously believed, with 80 per cent of advertisements targeting foreign workers offering wages below legal rates.
Little research or official data exists on how many temporary foreign workers and students are employed in Australia, let alone how many are being illegally underpaid.
The Fairfax Media investigation surveyed Mandarin-language websites, where it was common for jobs to be openly advertised at $10 to $13 an hour, significantly below Australia's legal minimum wage of $17.29 an hour.
A comprehensive study of 1071 job advertisements aimed at temporary foreign workers, largely from China, Malaysia, Hong Kong and Taiwan, show the vast majority offer work either below the minimum wage or below the award.
Some of the Chinese language advertisements openly admit they are offering "black" work, which signifies it is an illegal job.
Illegal underpayment is not confined to particular industries, and is evident across a wide range of low-skilled or semi-skilled jobs.
If the results were replicated across the variety of Australian visas used by students and temporary foreign workers, it's likely hundreds of thousands of people are being illegally underpaid.
At the extreme end, the investigation uncovered workers paid as little as $4 an hour, and shady networks of middlemen who demand payments from prospective foreign job seekers to secure work.
Fairfax Media has spoken to one job-seeker, who does not want to be identified, but who said he received death threats from a middleman.
The labour hire middlemen often take a cut from three sources: the workers themselves, the employers who hire the workers, and from the owners of the cheap hotels that house them.
In Mildura, Victoria, one middleman who hired out workers to local farmers also owned a caravan park, where he housed four workers per tiny room.
The National Union of Workers (NUW) has called for urgent action on the labour hire middlemen at the centre of many of the employment scams.
"If you sell alcohol you need a licence; if you want to trade people you need nothing," said Tim Kennedy, the union's national secretary. "Labour hire is completely unregulated, all you need is a phone and a spreadsheet to be a labour hire provider."
At the end of last year, there were more than 750,000 foreigners in Australia with temporary work rights, mostly on student, working holiday and 457 visas. The Fair Work Ombudsman estimates there are just under 600,000 visa workers in Australia.The number of temporary visa holders has more than doubled since 2000 and has risen sharply from negligible levels in the mid 1990s.
This is a starkly different labour market to that which greeted the surge of migrant workers after World War II. Back then, newcomers typically had permanent residency and far greater legal and work rights than today's foreign workers on visas.
In the modern era, some visas require the worker to retain the support of the employer to stay in Australia and, in the case of student visas, also include restrictions on the hours worked a week.
The abuses were graphically highlighted by the recent Fairfax Media/ABC investigation into rorts at the 7-Eleven chain, as well as an earlier ABC Four Corners program that focused on the agriculture sector.
The latest investigation, published today, indicates the problem is systemic, with sectors of the Australian economy increasingly reliant on illegal underpayment.
One Mandarin speaking middleman from Malaysia, who recruits farm workers, openly admitted the work was "black" labour, which in the Chinese community means illegal. When asked if he minded other job-seekers being told this, he said: "It is no problem to admit it. I don't want the job seekers [to] misunderstand the position."
Other advertised jobs demand workers pay $3.30 an hour from their wages, or several hundred dollars in up-front payments.
In some cases workers accused the advertisers and middlemen of promoting scams and fake jobs to steal from them. Poor English skills, a lack of local knowledge, and a fear that speaking out would result in them being forced out of Australia, contributed to the problem, foreign workers say.
Labor elder statesman, and its former national president, Greg Sword, said employers needed to be made responsible for the underpayment of workers.
"There also needs to be legislative change so that employers cannot avoid their responsibilities ... even though the middleman may be paying workers $10 an hour, if it's exposed, the employer should be held responsible."
The results of the Fairfax Media investigation showing 80 per cent of jobs were illegally underpaid are likely conservative. The investigation was based largely on an analysis of websites and Facebook pages. It did not count jobs where no pay rates were disclosed. If such jobs were included in the results, it is likely the level of underpayment would be even higher.
*Additional research and reporting by Monash University journalism students Yanzhu Xu, Luke Mortimer, Ivy Yuan and Sunny Liu.