North Korea has the largest number of modern-day slaves in the world, with just over one in 10 of the population subjected to forced labour at the hands of the repressive state.

The shocking abuse, which includes young schoolchildren being coerced into exhausting manual work, is outlined on Thursday in the newly released 2018 Global Slavery Index, the largest survey in the world of human slavery and forced marriage.

Based on 71,000 individual interviews in 48 countries, the report by the Walk Free Foundation – a human rights group campaigning to end slavery – concludes that an estimated 40.3 million men, women and children are still being forced to work against their will.

About 2.6 million of them toil unseen behind the closed borders of the Hermit Kingdom. Such is the extent of their mistreatment that the Foundation dedicated a spin-off report specifically to shine a spotlight on their plight.

Of 50 defectors interviewed over the course of a year, all but one described servitude either as children or adults, or in some cases both.