More than 45 million people around the world are trapped in modern slavery - a third more than previously thought, a major new report has found.
They are being trafficked and forced to work as prostitutes, domestic servants or enslaved in debt bondage and forced to work in factories and farms, according to the study.
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 18.35 million followed by China with 3.39 million and Pakistan with 2.13 million.
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.
He said: "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 45.8 million men, women and children are modern slaves - 10 million more than the last survey in 2014. Forrest said the rise was down to better and more data, although he said he also believes the number of those enslaved is increasing.
He said: "It isn't necessarily that fact that slavery has increased, we can't prove that, what we can prove is that the metrics of visibility, the hard data, is better.
"Although my gut feeling is that it is actually increasing still and it will be a year or two before it turns around. But it is going to turn around, the way the world is waking up to it."
The Home Office estimates that around 13,000 are in modern slavery in Britain. Out of these people, the largest proportion is from Albania followed by Nigeria and Vietnam, but many are British nationals, often teenage girls groomed and then forced into sex work.
While the report singles Britain out for praise, it warned that conviction rates remain low and immigration rules tying migrant domestic workers to their employers leave them more vulnerable to exploitation.
Fiona David, head of research at the Walk Free Foundation, an Australian-based NGO, said the refugee crisis sweeping through the Middle East and Europe has left people vulnerable to traffickers, but stressed that many people entrapped in slavery in Britain are themselves British.
She said: "The first thing to note is that modern slavery is not always of migrants, we have seen here in the UK some of the highest profile slavery cases have involved enslavement of British people or commercial exploitation of children who are themselves British.
"But of course, people moving in highly distressed situations have many risk factors. It is too early to say yet whether that is impacting on our estimates, I think we will see the results of that flowing through into the next global slavery index."
She said there is "huge variety" in the response of governments to tackle modern slavery, with some rich countries such as the Qatar failing to take adequate action. "This is an issue that every country has a responsibility to act on, every country could do more," she said.
Hollywood actor Russell Crowe will host the report's launch in central London on Tuesday morning.