There are around 450 criminal gangs around the world making money from images of child sex abuse, the UK's Internet Watch Foundation has said. The watchdog's annual report says that the 10 most prolific of these account for more than 650 web pages. But despite these gangs being well-established online, the IWF says the the industry is not growing. To help obscure their movements, they move their distribution networks regularly between different providers and countries. Most of the gangs operate a pay-per-view system, charging a monthly fee of around 55 for access to images and videos. Critics have accused the IWF of being ineffective, partly because it is separate from the police and partly because much of the illegal material online does not originate from the UK. IWF spokeswoman Sarah Robertson admits that it is not a policing body but denies that means it cannot act. The amount of child abuse content hosted in the UK has fallen from 18% to 1% in the last seven years," she said. It is important to remember the serious nature of the content the IWF polices, she said, and that behind every image is a child being abused. Some 44% of the content highlighted to the IWF last year depicted the rape of a child and 23% of it featured children below the age of six.