Children are developing permissive attitudes to sex and are viewing women as objects after being raised on a "diet of pornography", a major British study has found.
For the first time, the Children's Commissioner for England has found a clear link between exposure to extreme images at a young age and a rise in "risky behaviours".
It emerged that children who regularly viewed pornography were more likely to have underage sex, develop "casual and hedonistic" attitudes, experiment with drink and drugs and indulge in sexting, when explicit pictures are taken and sent to others using camera phones.
Boys were much more likely to be exposed to pornography than girls, it was found, resulting in "beliefs that women are sex objects".
The study, based on a large-scale review of international evidence, also found some evidence of a relationship between explicit images and a rise in sexual aggression and harassment of the opposite sex.
Dr Maggie Atkinson, the Children's Commissioner, warned that "violent and sadistic imagery" was readily available among "very young children" because of easy access to the internet on home and tablet computers and mobile phones.
It was claimed that many children from the age of 10 accidentally accessed "violent and sadistic imagery" while undertaking legitimate research.
"For years we have applied age restrictions to films at the cinema, but now we are permitting access to far more troubling imagery via the internet," Dr Atkinson said.
"We do not fully understand the implications of this. It is a risky experiment to allow a generation of young people to be raised on a diet of pornography."
The report called for compulsory sex and relationship education in primary and secondary schools, including modules on the dangers of pornography.
It follows claims by the National Association of Head Teachers and Ofsted, the education watchdog, that too many sex education lessons are of poor quality.
Speaking at the publication of the report in London, Sue Berelowitz, the Deputy Children's Commissioner, called on parents to avoid taking a "zero-tolerance" attitude towards pornography, saying that hard-line rules prevented children raising legitimate questions when they do access sexual images.
She added: "Education is the only universal lever we have to ensure all children are safeguarded against the possible impact of pornography."
The study - carried out by the universities of Middlesex, Bedfordshire, Canterbury Christ Church and Kent - was based on analysis of 276 pieces of research. One UK study found that 80 per cent of young people believed watching pornography "affected the way they had sex". It quoted other studies that found a relationship between explicit materials and "higher acceptance and engagement in sexually permissive behaviours" and "attitudes to sex that are casual and hedonistic rather than affectionate".
It also found a link to under-age sex and the likelihood of smoking, consuming alcohol and taking drugs.
One Swedish study found a quarter of young people who "consumed pornography" had at least one sexually-transmitted infection, while a Dutch paper said: "Exposure to sexually explicit online films was significantly related to the belief that women are sex objects".