Exposure to internet pornography leads teenagers to lose their virginity at a "much younger" age, researchers have found. A peer reviewed study from the journal CyberPyschology and Behaviour revealed that males aged between 12 and 17 who regularly viewed porn had sex at an earlier stage in their lives and were more likely to initiate oral sex, apparently imitating what they had watched.

Scottish experts warned that the rise in the viewing of pornography was implicated in a variety of sexual problems - including a rise in levels of STDs and teenage pregnancies - and called for parents to be more aware of what their children were watching.

Shane Krauss, a psychologist working from Castleton State College in Vermont, surveyed hundreds of people and found that men who had watched pornography between the ages of 12 and 17 were sexually active before those who hadn't. Women who had watched pornography at similar ages - a lower percentage than men - becamesexually active slightly younger.

Krauss said: "The internet is having some kind of accelerant effect, influencing and changing behaviour. Males are having oral sex and losing their virginity much younger when they are exposed to pornography, sometimes by a good three or four years for oral sex or two years for their virginity."

Catherine Harper, representative of Scottish Women Against Pornography, has worked with young people at the sexual health charity the Brook Advisory for 11 years. She claimed certain forms of venereal diseases - such as chlamydia of the eye - had been spread by men coercing their partners into performing sex acts copied from pornography.

She said: "The internet is where you get the most extreme stuff, sometimes live and in action, and it serves to normalise abusive acts."

A rise in rates of oral sex has been linked to an increase in numbers of tongue, mouth and throat cancers caused by the sexually transmitted human papilloma virus. Rates of the disease are at a 30-year high and are particularly prevalent among young men.

Sue Maxwell, a psychosexual therapist at Relationship Scotland, said she felt young men were too often getting their sexual information from pornographic websites rather than the many "excellent" sites set up by the government.

She said: "Men are affected by internet sexuality more than women. Instead of developing a relationship based on thinking what do you want, what do I want,' they go for something that gives them another high and in to compulsive behaviour, seeking out another sexual experience more sexually enthralling than the previous one.

Sex education in schools is insufficient, claimed Anna Martinez, head of the Sex Education Forum. She said: "Young people continue to tell us that there is a big gap between the sex education they need and the sex education they are getting in school, and from parents.

"In the absence of good quality sex education, it is little wonder they turn to alternative sources of information including porn in the search for answers."