One of the world's leading workers' rights groups has revised upward its global estimate of the number of people working in forced labor.
Almost 21 million people are now in forced labor, according to the new study from the International Labour Organization.
That is up from a "minimum estimate" of 12.3 million in ILO's similar report in 2005 - but the group says the increase is down to better research methods rather than indicative of a trend.
It is not possible to know exactly how many people are enslaved - different experts have different numbers, partly because of different counting methods.
The ILO, a U.N. agency focusing on labor rights, said its figures show three in every 1,000 people worldwide are in some form of forced labor - from state-imposed work to forced sexual exploitation.
Beate Andrees, head of the ILO's Special Action Programme to Combat Forced Labour, said that attention should now concentrate on better identifying and prosecuting offenses around forced labor such as human trafficking.
She said: "The successful prosecution of those few individuals who bring such misery to so many remains inadequate – this needs to change.
"We must also ensure that the number of victims does not rise during the current economic crisis where people are increasingly vulnerable to these heinous practices."
In a news release, ILO said that of the 20.9 million globally in forced labor, 4.5 million were sexually exploited and 14.2 million were exploited in industries such as construction and agriculture.
It said the Asia-Pacific region accounts for the largest number of forced laborers in the world – 11.7 million – and Africa the second highest number at 3.7 million.
ILO's report also said 9.1 million victims were moved either internally or internationally.
Andrees said: "We have come a long way over the last seven years since we first put an estimate on how many people were forced into labor or services across the world.
"We have made good progress in ensuring most countries now have legislation in place which criminalizes forced labor, human trafficking and slavery-like practices."