Our national reluctance to educate children frankly about sex has less to do with protecting their innocence and more to do with adults’ own sense of shame about the topic, according to the author of an explicit new sex education book.

Ann-Marlene Henning’s Sex and Lovers: a practical guide has been described as The Joy of Sex for the new generation. But while the 1970s manual famously had line drawings of naked-yet-hirsute lovers, Henning’s book includes photographs of real-life sexual partners having real-life sex.

Though artfully shot, and largely involving young, attractive people, the photos are unquestionably explicit. As well as full and oral sex, there are photos of gay couples: a woman sucking on her girlfriend’s breast; two men kissing.

“They’re just having normal sex - that’s it,” Ms Henning, a Danish neuro-psychologist who now practises as a sexologist in Germany, says of the photos. “We need pictures like that. All that internet porn stuff is too rough, too fast, and just strange-looking people. Too much, too much.

“One of my big messages is to teach young people that this is a normal topic. Why is it, then, that I can’t show normal people having normal sex? They only have to go home, to leave the classroom - or maybe not even that - to see something worse on their mobile phones.”

Once, when giving a talk to students at a German school, Ms Henning attempted to show how something as innocuous as searching for Disney films online could bring up porn websites. She accidentally set off a succession of pornographic pop-up windows. The only way to stop it was to switch off the computer. Afterwards, a 12-year-old boy offered her this reassurance: “Oh, God. It happens all the time.”

“But that’s what the parents don’t want to know,” Ms Henning tells TES. “Parents don’t like to know that their children have seen this. What’s missing are some acceptable grown-ups - parents, teachers, doctors - who can talk about sex in a normal voice, maybe with a little humour, in a normal, pragmatic way. Just give young people a frame for what’s out there.”

The reality, she says, is that more and more adolescents are coming into her practice concerned that they are unable to perform as quickly and as voraciously as the participants in online porn. “They think they can always have an erect penis,” Ms Henning says. “Men who can’t do that feel inadequate. And women think that they must always be quick to be aroused and must always have an orgasm.”

Part of the problem is that adults are often ill-informed themselves. She gives the example of a 52-year-old biology teacher who said the clitoris was either the size of a pea or a hazelnut. In reality, it averages around 9cm, most of it inside the body. “She’d never heard that there’s as much inside as outside,” Ms Henning says. “And she’s the one teaching the little ones.”

She would love, therefore, to see her book used in school sex education lessons. Its written content, while less attention-grabbing than the pictures, delivers biological information, messages of self-acceptance and technical tips on how to make sex an enjoyable experience for yourself and your partner.

“It’s not only about sexuality,” Ms Henning says. “It’s also about finding yourself as a human being. It’s about feelings, actually. And what they’re learning from porn is sex without feelings. I think we have a responsibility to teach them, even if it’s uncomfortable for us. Because all we’re doing is protecting our own shame.”

She acknowledges that it would be an extremely brave teacher who unilaterally decided to introduce Sex and Lovers into a sex education lesson. After all, simply delivering sex education continues to be controversial even in the 21st century.

When, last month, Labour MP Diana Johnson introduced a bill into Parliament intended to make sex and relationships education compulsory, a Conservative MP responded by saying that sex education, as a concept, had “failed”.

“As we have had more sex education, the problem has got worse,” Philip Davies told Parliament during a debate about the bill. “One thing everyone will have to conclude is that what we need is less sex education, or perhaps even none.”

But Simon Blake, chief executive of sexual health charity Brook, thinks that this misses the point entirely. “It’s a mistake to focus the debate on sex education in schools,” he says. “We should focus on creating an open and honest culture for young people, where they go through adolescence and adulthood knowing that at some point they will have sex. We want to prepare them for doing it consensually and respectfully.

“We’ve got to get a grip on it. Grow up, take a deep breath and start respecting and trusting young people, working in partnership with them to give them what they need.”

Throughout history, he says, visual guides such as the Kama Sutra have served as useful how-to manuals for sexual novices. And now, more than ever, books such as Sex and Lovers play an important role.

“In a world which is incredibly visually stimulated, there’s a constant stream of beautiful people, with beautiful bodies, doing amazing things - whether jumping out of an aeroplane or having sex,” Mr Blake adds. “We have to find ways to engage with young people. Show them what it looks like and what it feels like having sex. I think the principle of finding egalitarian, consensual ways of showing young people what sex is, what relationships are, is an important one.”

Ms Henning encourages sex education teachers to group together and to invite parents into school to discuss her book. Some parents, she acknowledges, will doubtless be unenthusiastic. But that reluctance needs to be put into context: if schools do not teach children about sex, porn will.

“If you don’t teach young people, you take away their rights,” she says. “I’m entitled to learn about things that will develop my sexual growth and my human living. What is it that’s so dangerous about this book, given that we know what they’ve already seen?

“What argument is there for not showing them this book? `I’m ashamed’?” Her tone becomes sarcastic. “Yeah. That’s a good argument. They are grown-ups, and they can’t stand the topic. So, I ask, who are we protecting, then?”

Sex and Lovers: a practical guide by Ann-Marlene Henning and Tina Bremer-Olszewski is published by Cameron amp; Hollis. Find out more at www.sexandlovers.uk

What the book says.

.about sexuality

“The first time just thinking about something makes you excited, or the mere brush of a finger turns you on, your sexual personality - the sexual you - starts to take shape. This side of your personality can develop in a strikingly different way from the rest of you.It’s good to know as much as possible about your own sexuality, and to be aware of how your sexual personality expresses itself. The better you know yourself, the better you’ll handle your sexual preferences and desires as well as your fears and insecurities.”

.about seduction

“Nowadays, it is increasingly unusual in developed countries for a girl to wait for a boy to make the first move. Girls can, and do, take the first step. The important thing is to have received a positive signal from the person you’re interested in.Usually people start by swapping interested glances.At this point, both of you need to be as brave and as unambiguous as possible.”