The ease with which hardcore pornography can be accessed online means almost all 14 to 17-year-olds will be exposed to it at some point, according to research.
And the younger a person starts watching pornographic material, the earlier they have sex, writes Oliver James in The Guardian.
Research carried out in 2005 found that 93 per cent of boys and 62 per cent of girls had viewed pornography by 18, and Mr James believes new free websites will have increased the figure.
The phenomenon is also damaging to marriages, with married women more likely to feel distressed at their husbands’ use of internet pornography.
“Common difficulties identified from porn use are that the user starts demanding different kinds of sex, is much less loving and uses the partner as a toy”, Mr James writes.
Last week the director of a rape crisis centre warned that the increasing use of adult images in youth culture is making it difficult for young people to say “that’s not right”.
Dr Catherine White said: “There’s an increasing sexualisation of children. When you see a little girl wearing a T-shirt with a Playboy bunny, that’s wrong isn’t it?
“I’ve seen another that said ‘Porn star in the making’.”
She added: “It might not be one thing but all together it’s having an effect on values, on what is acceptable and not acceptable.”
Earlier this month it was reported that teenagers are increasingly involved in ‘sexting’ – distributing a pornographic image via mobile phone.
The charity Beatbullying found that more than a quarter of all eleven to 18-year-olds had received explicit photographs by text.
Often the images are sent by teenage girls to their boyfriends, who then distribute them to friends. The images are often posted online, and can end up being circulated by paedophiles.
The Child Exploitation and Online Protection Centre said: “Paedophiles are actively looking for these pictures and then using them as leverage.
“The message is, if you do not want the image to be seen by other people, don’t take it.”