Edward first discovered porn when he was 13-years-old at school. Every now and then his friends would come in with new videos and websites that they had dug up online the night before and share them around. Only a year earlier his contemporaries might have been swapping toys. Now they were trading porn.

"I started watching it more and more," the 19-year-old recalls. "It had a massive effect on the way I thought about sex and has been hugely detrimental to my perception of what a relationship is supposed to be like."

By the time he got together with his first girlfriend, three years later, he felt utterly confused. "It wasn't that I was expecting sex in real life to be like that in porn, or that women would be like those you see in the videos. But I had a very distorted view on relationships."

Alisha, who first watched erotica in her early teens at a friend's house, was also left perplexed. The east Londoner worried about her body image and whether boys would have unrealistic expectations of what sex could be.

"Every time I saw porn I thought that I wasn't sexual enough, that I wouldn't be able to act like that," the 21-year-old recalls. "It wasn't until I was much older that I realised it is not supposed to be that way all the time, that porn doesn't show a typical sexual encounter."

Debates on porn are often passionate. What was considered pornographic in the 1970s, when conservatives blamed Playboy magazine for a third of divorces in the United States, would barely raise an eyebrow now. And when the internet brought porn into our homes en masse in the late 1990s, doomsayers predicted society's moral collapse – even as rates of divorce, abortion, teen pregnancies and sexual violence fell across Western nations. Yet parental concerns remain entrenched and politicians are more than happy to tap into our fears that we risk sleepwalking towards a society addicted to silicone-enhanced sex. In the recent Republican primary debates, candidates virtually tripped up over themselves to be toughest on smut with Rick Santorum suggesting a complete ban on pornography.

The UK debate is less shrill but shows no signs of fading as parents fret about what children get up to online. The debate focuses on who is responsible for stopping children and teenagers from accessing porn. Should internet service providers force customers to "opt-in" to unrestricted access, or should the onus be on parents to keep an eye on what their children are up to online?

One of the few areas where both sides of the argument agree is the huge accessibility of porn compared to the days when top-shelf magazines, peep-shows and blackmarket videos were the only way teenagers could get visual titillation.

Around a third of all web traffic is now porn-related with various studies suggesting up to two-thirds of men and one- third of women under 50 regularly view erotica. There is little doubt teenagers can access porn like never before. Depending on the study you read, between 40 to 80 per cent of 10- to 17-year-olds have viewed porn, mainly through smartphones and home computers.

But there is far less consensus about the effect porn has on society and our children. Specialists and rehabilitation centres say the palpable increase in adults and teenagers seeking help for porn addiction cannot be ignored.

"Feedback from our counsellors shows that we are seeing more and more people for whom pornography is impacting on their relationship," says Kim Atkins, from the counselling charity Relate.

Successive studies have shown that violent or abusive porn makes up only a fraction of what is available on the internet and yet concerns abound that an entire generation of children are growing up to believe that anal sex, threesomes and bondage form part of an everyday physical relationship.

Yet research suggests we might not be giving teenagers the credit they deserve in being able to differentiate between fact and fantasy. A recent study of 73 middle-class Swedish teens in the Journal of Sex Research – one of only a few papers to explore teenage porn use in the age of smartphones – found most participants "had the ability to distinguish between pornographic fantasies on the one hand, and real sexual interactions and relationships on the other".

Paula Hall, a founder member of the Association for the Treatment of Sex Addiction and Compulsivity (Atsac), agrees. "To suggest that teenagers can't tell the difference is insulting their intelligence. They can watch violent DVDs and know that's not how you behave... Porn is cartoon sex and the vast majority of teens see that. But for those who have a predisposition to addictions, they have access to this drug, if you like, with no education or awareness that it can become a problem."

Rather than try to ban pornography or shut down the internet – both of which are all but impossible – many believe parents and schools must become more proactive at educating children about pornography and consensual sex. A recent survey by Psychologies magazine found only 25 per cent of parents talked to their children about porn.

Simon Blake, chief executive of Brook, a charity that provides sexual health advice to teenagers, says: "Parents should be talking to young people about pornography because they will always want to find out about sex."