A report by the NSPCC has described the volume of people viewing online images of child sex abuse as a "social emergency", with the numbers of perpetrators potentially as high as more than half a million. This estimate is vastly higher than the number of offences that have actually been recorded, which themselves have more than doubled in recent years.

The estimate, which was described by the National Police Chiefs' Council lead for child protection as "shocking", was based on a German study which detailed self-reported sexual interest in children. The NSPCC then applied the figures to the UK.

The report found: "If we were to apply the same level of self-report data to the male UK population ... and applying standard statistical techniques to calculate a confidence interval, this would equate to an estimate that there may be between 450,000 and 590,000 males aged 18-89 in the UK who have at some point viewed and used child sexual abuse images."

Additionally, in 2015, 68,092 URLs were taken down by independent watchdog the Internet Watch Foundation, representing a rise of 118% over the previous year.

NSPCC chief executive Peter Wanless said of the findings: "The sheer numbers of people viewing child sexual abuse images online must be addressed as a social emergency.

"It is two years since the government made it a national priority to rid the internet of these vile crimes against children, but today's report reveals how horrifyingly prolific the problem remains.

"We should be long past the point when there are dark corners of the internet where these terrible crimes against children are hosted for the pleasure of paedophiles."

While the NSPCC said it recognised that progress has been made, it stressed that further measures are needed to protect vulnerable children. These include UK internet firms signing up to codes of behaviour, an independent annual audit of the current self-regulatory framework, and an annual government transparency report on the identification and removal of child abuse images.

Earlier this year the NSPCC warned of other online threats to minors, including the grooming of young children. It also warned of the risks of children being exposed to online pornography.

NSPCC says sex abuse against kids rising
The NSPCC has recorded a 35% rise in the number of young people contacting its Childline service for anxiety problems NSPCC.org.uk