More than 45 million people around the world are being trafficked and forced to work as prostitutes, domestic servants or enslaved in debt bondage and compelled to toil away in factories and farms, according to the study.
Anne Reid is the territorial director of trafficking and modern slavery at the Salvation Army. She told Premier's News Hour: "We are getting much better at really focusing on what we mean by slavery and really ensuring that we're identifying the right people.
"Slavery has many forms, I would suggest it's only limited by the imagination of the traffickers, in that if slave traders can think of a way of exploiting somebody then they will use that way".
The Global Slavery Index for 2016 found that every corner of the globe is affected by slavery, but Asia is the worst offender.
The highly secretive country of North Korea had the highest prevalence with 4.37% of its population enslaved, followed by Uzbekistan at 3.97% and Cambodia with 1.65%.
India has the highest number of modern slaves with an estimated 18.35m followed by China with 3.39m and Pakistan with 2.13m.
The report hailed the UK as having "led the world" in its anti-slavery strategy. The 2015 Modern Slavery Act toughened up laws and increased the sentence for the worst offenders to life imprisonment.
Andrew Forrest, chairman and founder of the Walk Free Foundation, which compiled the report, urged world leaders to follow Britain's example.
Speaking ahead of the report's launch in London later on Tuesday, he told the Press Association: "One of the reasons why we chose to launch the Global Slavery Index 2016 in London was because of the leadership which Britain has made on the modern slavery issue.
"The Modern Slavery Act 2015 led the world and we are seeing this having a real impact in how companies and countries behave. We feel very strongly that if this leadership is adopted by the nine other major economies of the world then the world would be a much safer place."
The report found that 45.8m men, women and children are modern slaves - 10m more than the last survey in 2014.
Mr Forrest said the rise was down to better and more data, although he said he also believes the number of those enslaved is increasing.