The Baptist World Aid Australia analysis of more than 500 local fashion houses found 87% could not provide evidence of paying a living wage to workers in overseas supply chain facilities.
According to the federal government, 97 per cent of the nation's textiles are designed and manufactured overseas, mostly in low-cost nations such as China and Vietnam.
The report found that in "final stage" factories where tasks such as assembly, cutting, sewing and printing were performed, a living wage - in some cases less than $180 a month - was paid in only 3 per cent of cases.
Many brands conceded a failure on baseline pay beyond direct suppliers, despite having labour rights policies in place, it found.
The worst performers on ethical production were surf, skate and streetwear, ultra-fast fashion, and footwear brands.
Report author Katherine Halliday said local brands had stalled on delivering better pay to factory workers, despite promises.
"Brands are getting better at talking about sustainability, but that talk isn't translating to real change on the ground," Ms Halliday, advocacy lead at the not-for-profit Christian group, said.
"Indicators like supplier tracing and living wage have sat at the same level for years, and brands are repeating the same commitments from one report to the next," she said.
"Companies are getting better at their policies and their modern slavery and sustainability reports but they might be falling short of real progress for workers."
The long-term problem was being amplified by Australia's cost of living squeeze, she said.
"Both shoppers and brands are turning to cheap clothing to keep up with trends, and we're seeing a concerning trend towards complacency and a lack of accountability across the industry," Ms Halliday said.
With the majority of clothing and footwear made in developing nations, companies could afford to pay workers more without passing on costs to consumers, she said.
"If a company were to pay the workers that made their clothes a living wage, the price tag for a consumer would not jump as much as we expect."