One of the country's most famous wine districts has been raided as part of a national crackdown on the illegal cash economy.
Federal authorities have staged surprise inspections of 18 vineyards in South Australia as they investigate unlawful labour practices and exploitation of seasonal workers.
Regulators have combed vineyards at the Barossa Valley, Adelaide Hills and McLaren Vale in recent weeks, quizzing workers, managers and labour-hire providers.
The landmark crackdown has also requested detailed records including any labour-hire contracts, invoices, timesheets, pay slips and work rosters as part of the raids.
No details of alleged breaches or enforcement actions have been released, but the Australian Tax Office said investigations were ongoing.
Unlawful labour practices could cause significant disadvantage to honest operators in the viticulture or grape industry, ATO assistant commissioner Tony Goding said.
"Paying workers off the books, ignoring ATO obligations or using dodgy labour-hire providers doesn't just break the law, it erodes trust in the viticulture industry," he said.
Vineyard owners must take responsibility when outsourcing their workforce, he said.
"If the cost of labour looks impossibly cheap, there's usually a reason and it's rarely legal,'' he said.
Operation Zephyr, which involves the ATO, Fair Work Ombudsman and Border Force agents, is using data analytics and intelligence to identify high-risk employers.
It is part of the Shadow Economy Taskforce, which is targeting businesses that evade tax or exploit the regulatory system.
Fair Work Ombudsman Anna Booth said there were large numbers of vulnerable workers in grape picking, packing, and pruning vineyards.
''Migrant workers must remember that they have the same workplace rights under the Fair Work Act as other employees in Australia, and protections exist for their visa if they call out any breaches to us,'' she said.
Border Force Commander John Taylor said migrant workers were essential to SA's viticulture industry and regional economy.
''There's no place for employers who exploit them," he said.
''Exploiting vulnerable workers or misusing the visa system is unacceptable, and the consequences can be serious.''
