Two-thirds of surveyed Australian working-holiday visa holders felt they were taken advantage of by employers.
The Fair Work ombudsman released an extensive survey of more than 4000 people who had been granted a second-year 417 visa on Saturday.
About 66 per cent of those felt employers took advantage of visa holders.
The report found some people had been sexually harassed, had their passports withheld or had their wages unlawfully deducted.
Ombudsman Natalie James said Australia was at risk of it being a “black-market, exploited labour-force” if nothing changed.
“While many 417 visa-holders who work in Australia have a positive experience, many are being subjected to underpayment or non-payment, unlawful deductions ... and other forms of exploitation,” Ms James said.
In 2015-16, $79,153 in unpaid wages was recovered for 34 workers in Launceston and the North-East, according to the ombudsman.
Tasmania-wide, $464,609 in wages was recovered for 152 people in 2015-16.
The temporary 417 visa is issued to young people who want to work and holiday in Australia.
To be eligible, the person must undertake 88 days of paid work in a regional area within the agriculture and aquaculture industry.
The inquiry recommended more education and research into a culture of compliance is undertaken.