Underpaying migrant workers has become a business practice for unscrupulous employers.

For some employers, it is an easy way to boost the bottom line with a low risk of getting caught — hence there is little incentive to comply with industrial laws.

It has even been described as a "business model" by worker advocates.

"There are employers out there structuring the cost of doing business through stealing wages," said Ged Kearney, president of the Australian Council of Trade Unions (ACTU).

"They use very exploitable migrant workers, and use the sickle of [the workers'] temporary visa status to enforce that."

Out of the 900,000 temporary migrants in Australia with work rights, those in the 457 visa category are a particularly vulnerable group — as many are hoping to attain permanent residency.

Getting away with wage theft

The ABC was able to interview Ben, a Sydney-based technician who is on a 457 visa (and who wanted to use a pseudonym instead of his real name).

Unfortunately, he is working for an employer who commits wage theft by routinely blackmailing him.

However, Ben chose not to complain to the authorities because the employer also regularly threatens to "get him fired" and "deported".

"My boss deposits [my salary of] $1,500 into my account each fortnight, then I have to withdraw $500 from an ATM to give back to him," he said.

"I was never in a position to refuse — otherwise, he wouldn't offer me the 457 visa."

Ben is ultimately forced to survive on $500 per week in Sydney, the city with the most expensive real estate in Australia.

But he is worried about the consequences of getting sacked before he attains permanent residency.

Under Australian immigration laws, 457 visa holders are allowed to remain in the country for only 60 days from the date their employment ends.

"If I get fired, I have two months to find a new job — otherwise I'll have to leave the country," Ben said.

"The immigration department told me I just have to find another employer."

Back in April, the Turnbull Government announced it was abolishing the 457 visa scheme — and axing more than 200 jobs from the list of occupations that skilled foreign workers can apply for under the replacement scheme.

The silver lining for Ben is his occupation survived the cull, so he plans to apply for permanent residency after he completes two years of work with his employer.

Exploitation affects the economy

"At least two-thirds of migrant workers are exploited with regards to their pay and conditions," Ms Kearney said.

"If an employer can access a temporary worker, employ them for half the minimum wage, exploit them to the degree we are seeing, that has to have an impact on the local employment market."

It also impacts other workers, forced to compete against those willing to work for less than the minimum wage — which is $22.13 for a casual worker.

Such practices place downward pressure on wage growth.

"Low wages in Australia has been a big issue over the past five years," economist Callam Pickering said.

"It has actively undermined household spending, keeping it at record low levels.

"It has also kept inflation low [and] forced interest rates to their lowest levels in history."

The 7-Eleven scandal was just one recent example of a business, which systematically exploited migrant workers.

One in three migrant workers, who identified as backpackers and international students, are paid about half the minimum wage, according to research released this week by the University of New South Wales and UTS.

The study also showed most foreign workers are fully aware they are being exploited.

In addition, it found restaurants, cafes and farms — which employ fruit pickers — were workplaces which had some of the worst levels of underpayment.

"Visa workers represent 18 per cent of all the requests for assistance we receive," Fair Work Ombudsman Natalie James said.

"Given they are only about 6 per cent of the labour market, that does tell you they're over-represented in the cohort of people who aren't being paid correctly in the workforce."

Tougher penalties for employers

Ms James said the visa status of migrant workers, who complain to the Fair Work Ombudsman's office, will not be jeopardised.

"We can work with the Department of Immigration to ensure your visa is not affected because you've taken action to enforce your rights under the law to be paid your minimum wages."

In September, the Federal Government introduced the Fair Work Amendment (Protecting Vulnerable Workers) Act which increases penalties for employers' serious breaches of industrial law.

"Now if a corporation rips off a visa worker and we can prove it was deliberate and systematic, that corporation will be up for over $630,000 potentially per breach," Ms James said.

"If you don't want to proceed, you will have that choice. But if you do, we can work with the Department of Immigration to ensure your visa is not affected because you've taken action to enforce your rights under the law to be paid your minimum wages.

But that is provided the employer is caught, and successfully prosecuted.

"Ultimately, low wages and cutting those wages undermines the success of the Australian economy," Mr Pickering said.

"Bringing people into the country, paying them below minimum wage, is not a recipe for economic success."

Becoming a permanent resident in Australia is the key to Ben's future.

As for why it matters to him, Ben explained: "It would give me the freedom to choose... to go back home by choice, and not because I'm forced."

If all goes well, he may also win the freedom to choose an employer who is willing to pay a fair wage — for a fair day's work.

If you have more information about illegal workplace practices, you can contact us anonymously.

Or if you have concerns about your work conditions, you can contact the Fair Work Ombudsman.