A dramatic surge in the number of online child sex abuse images uncovered in Britain has stoked fears about the growing sexual exploitation and enslavement of children worldwide via technology, anti-slavery campaigners said on Monday.

Britain's National Crime Agency (NCA) said it had received more than 82,000 referrals of child sex abuse images last year — up 700 percent from 2012.

At least 80,000 people in Britain are estimated to pose a sexual threat to children online, and a rising number are taking advantage of technology — from using the dark web to end-to-end encryption — to evade detection, say the police and government.