The findings were outlined in a new report released by the Australian Institute of Criminology, the first time the true extent of modern-day slavery in the country has been revealed.

Between the 2015-16 and 2016-17 financial years, the report estimates there were between 1300 and 1900 victims of slavery in Australia, such as those exploited into labour or sex and forced into marriage.

In the two-year period, just 414 of those victims were known.

"There are estimated to be four undetected victims for every detected victim in Australia, meaning that between 928 and 1493 victims remain undetected," the report said.

Australia has been the sixth nation in the world to produce an estimate to the number of modern slaves in the country, with similar studies conducted in the UK, Ireland, the Netherlands and Romania.

While law enforcement agencies have kept track of the number of modern slavery cases reported to them, the report said estimating the true number of incidents in Australia had always been challenging.

"Many crimes do not come to the attention of authorities and may not be recorded even if reported," the report said.

"This is compounded in the case of modern slavery, where the collection of statistics is affected by the clandestine nature of these crimes, low reporting due to mistrust in authorities and fear of deportation."

Head of research at the Walk Free Foundation Jacqueline Joudolarsen said the report was important in highlighting the number of unreported victims.

"It tells us we need to step up efforts to identify victims," Ms Joudolarsen said.

"We've come a long way in terms of raising awareness and we still have a long way to go. For lots of people, slavery is very much considered a thing of the past, but it couldn't be further from the truth."

Ms Joudolarsen said the anti-slavery foundation had seen a range of female and male victims, most being around 18 to 30 years old.

"It's happening in a range of industries such as agriculture and construction, cleaning and domestic work," she said.

"Migrant workers or those on temporary visas tend to be more vulnerable because they're more dependent on their employer and often work in remote and regional areas."

Of the cases reported to federal police in 2016-17, nearly half were cases of forced marriage, while 25 per cent were those exploited for labour and a further 13 per cent for sexual exploitation.

"Since 2013, AFP referrals reveal a substantial downward trend in the number of sexual exploitation cases at the same time as a substantial increase in the number of forced marriage cases," the report said.

Between 2004 and 2017, 841 human trafficking and slavery cases were referred to federal police, and 21 offenders were convicted.

The report's findings comes as new modern slavery laws came into effect from January this year, which required companies with earnings of more than $100 million to report modern slavery risks in their supply chain.

It's the second country in the world to introduce such laws, after the UK introduced similar legislation.

Lawyer and project manager with Anti-Slavery Australia Grace Wong said the new laws were a welcome step forward in combating modern slavery.

"It's an incredibly important step for Australia because it raises the profile and awareness of modern slavery and places the burden on businesses and government agencies to take proactive steps," Ms Wong said.

"Some of the businesses' practices might be leading to further exploitation, and the laws not only identifies the risk but takes steps to manage it."

A spokesman for the federal police said the agency was working to ensure more incidents of modern slavery were being reported.

"The AFP works in strong partnerships with government agencies, the community, non-government organisations and the private sector to prevent, detect and investigate human trafficking and modern slavery offences," the spokesman said.

"The AFP has specially trained investigators responsible for working with victims of human trafficking and investigating these offences.

"We hope this [report] can help victims to see they are not alone and encourage them to escape exploitative situations or come forward to police."