Extreme internet pornography is being blamed for the doubling of criminal convictions for rape by those aged under 17 in the last four years.

Recent cases include a 12 year-old boy who repeatedly raped his younger sister after becoming fascinated by internet pornography related to incest, and an 11 year-old boy who admitted seven counts of rape and sexual assault on boys aged under 13, attacks fuelled by viewing explicit images.

Last year a report from the NSPCC and the Children’s Commission for England revealed that 94% of children had viewed pornographic images by the time they were 14, and that more than 50% of boys aged 11 to 16 believed they were realistic depictions of sex.