More than 45 million people around the world are trapped in modern slavery, an annual study by an Australian pressure group has found.

The Global Slavery Index for 2016, published by Perth-based Walk Free Foundation, discovered that up to 4% of the population in some countries are in bondage of some kind.

Modern slavery includes people who are forced to work as prostitutes or domestic servants, or who are enslaved in debt bondage and compelled to work in factories or on farms.

Asia is the worst offender, the study found, with up to 4.37% of people in North Korea and 3.97% of the population in Uzbekistan enslaved.

The highest number of slaves in any one country is in India, which has 18.35 million, followed by China with 3.39 million and Pakistan with 2.13 million.

The Walk Free Foundation's founders say more countries should follow the lead set by the UK, which last year brought in the 2015 Modern Slavery Act.

Walk Free chairman Andrew Forrest 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."

A total of 45.8 million men, women and children are modern slaves, according to the study - 10 million more than the last survey in 2014.

Mr Forrest said the rise was down to better access to data, although he added that he believes the number of slaves is rising.

The Home Office says it estimates there are 13,000 modern slaves in Britain.

Out of those, the largest group is from Albania, then Nigeria and Vietnam.

But many are British nationals, the Home Office adds - most often teenage girls who have been groomed and then forced into sex work.

While the report singled Britain out for praise, it said that rates of conviction in the UK are low and immigration rules leave migrants vulnerable to exploitation.

Hollywood actor Russell Crowe will help launch the report in central London on Tuesday morning.

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