About a dozen activists staged a protest outside the theme park, waving a banner that read "No Disney Sweatshop Toys" and urging the US entertainment giant to improve working conditions.
Staff are paid 2.5 yuan (32 US cents) per hour, 62.5 percent of the legal minimum wage of 4.02 yuan, while overtime premiums are also below the minimum required by law, said the report compiled from interviews with 35 employees.
The study charges that managers fine workers five yuan for toilet breaks that exceed five minutes and 10 yuan for refusing to do overtime work.
The report also said workers in the paint spraying and pad printing departments complained that they were sometimes breathing in chemical and paint fumes for hours due to poor ventilation, exposing them to health risks.
The employees are not given insurance against work injuries, nor are they granted pensions, the study said.
The report includes pictures of filthy communal toilets in the staff dormitory, saying pipes are often blocked, causing waste to spill out.
Walt Disney said it takes "claims of unfair labour practices very seriously, and (will) investigate any such allegations thoroughly".
It admitted its own investigation had revealed violations at the Haowei factory, adding that action would be taken to rectify the problem.
"Disney is currently working on a factory remediation plan with the licensee who has placed orders with this factory," it said in a statement.
Hong Kong Disneyland, which opened on September 12, 2005, is struggling to attract visitors. The park would not disclose attendance numbers and would only say it has been given consistently high guest satisfaction ratings.