Modern slavery could cost NSW more than $9 billion and the state's anti-slavery commissioner wants key frontline services to help identify and assist potential victims.
A NSW parliamentary inquiry is reviewing the state's modern slavery laws and whether they are working as intended.
The state's Anti-Slavery Commissioner James Cockayne said modern slavery was "clearly occurring" in NSW, with the best available estimates suggesting there could currently be 16,400 cases.
"We estimate that the cost of the current victim caseload in NSW will run to as much as $9.6 billion," he said on Monday.
Dr Cockayne said existing laws took a "passive approach" to detecting and exposing instances of slavery, often relying on victims or members of the public to come forward with reports.
"Modern slavery is about the denial of voice and of agency," he said.
"It's a lot to expect somebody in that situation - someone who's being treated as if they are owned - to somehow find the opportunity and the means by which to come and express their situation."
The commission is working to develop the skills of law enforcement officials and frontline service workers to better detect potential cases.
Dr Cockayne said international research showed 84 per cent of people experiencing human trafficking would present to a frontline medical worker during the period they were being exploited.
"My office is looking to mobilise healthcare workers because we think they are another critical frontline cohort that has the opportunity to identify victims of modern slavery and help refer them to appropriate treatments," he said.
The commissioner said under current laws he was not able to investigate individual cases of modern slavery or attend a worksite where it may be occurring, unless he requested to do so through the employer.
"The experience of other authorities such as the Fair Work Ombudsman is that (attending) by request leads to a suppression of indicators or evidence of violations of workplace obligations or indeed criminal law," he said.
In 2018, NSW became the first state or territory in Australia to introduce standalone legislation to address modern slavery. It remains the only state with an anti-slavery commissioner.
Australians who are in or notice suspected modern slavery are urged to contact the commissioner's office or the Australian Federal Police.
Modern slavery can cover a range of circumstances including forced labour, debt bondage, forced marriage and human trafficking.
