A Belgian sex therapist and UN goodwill ambassador who believes that all children should get a qualification in sex education is to start a Jamie Oliver-style campaign to change the way British schools tackle the subject.

Goedele Liekens, a former Miss Belgium who presented the country's edition of The Weakest Link, believes the way sex education is handled in British schools is "hopelessly out of date" and should begin "properly and comprehensively" at an early age.

Much as Oliver used a television series to campaign on school dinners, Liekens is to use a new Channel 4 programme, Sex in Class, to argue for a GCSE in sex education.

The programme will feature Liekens visiting the classrooms and homes of British schoolchildren, working with 15- and 16-year-olds to put together the basis of what she hopes could become a properly approved GCSE.

Liam Humphreys, Channel 4's head of factual entertainment, said: "The way she looks at the world and sex education is going to be the most marvellous culture clash with even the most liberally minded British teacher. Some of the things acceptable [in other countries] – teaching 10-year-olds all about masturbation – is obviously going to stretch the boundaries of what is acceptable over here, but if you analyse what she is saying it makes complete sense."

Liekens has said the UK has been "too prudish for too long" about sex education. "England has just about the highest teenage pregnancy rate in Europe," she told a Belgian newspaper. "Now they have finally realised that it is best to teach youngsters about feelings, relationships and sex." She said the Channel 4 show would be a "kind of sex education programme for youngsters in which I will also involve their parents".

The programme, which will initially be an hour-long one-off but which Channel 4 hopes could become a series, comes at a time of growing concern at the rate of teenage pregnancies and sexually transmitted diseases among the young in Britain.

The Liberal Democrats said last week that all children in state schools should get lessons about sex and relationships from the age of seven.

State secondary schools run by local authorities are required to offer sex and relationships education, but there is currently no legislation for free schools and academies.

Countries such as the Netherlands and Sweden have been held up as examples of a more liberal and open attitude to sex education than the UK. In the Netherlands, sex and relationship education begins in primary schools for children as young as six. It has one of the lowest teenage pregnancy rates in the world.

British parents retain the right to withdraw their children from sex education classes, and surveys have frequently shown that many oppose school sex education for young children.

Humphreys, who talked about the show in an interview with the Guardian, said Liekens, 51, was "dynamite" and a "real star in the making".

As well as going into schools, she will visit pupils' homes to encourage them and their parents to talk about sex, because she believes that sex education should start at home.

Humphreys added: "It's completely copper-bottomed advice she is giving out, but it's also completely shocking because it's so out of character to hear that kind of language in a British school. She is going to investigate setting up a GCSE in sex education."

Liekens, who has been called the "leading lady in sexology", has written several books including The Vagina Book, The Sex Bible and Her Penis Book.

Another book, Start 2 Sex, attempts to answer teenagers' most frequently asked questions about sex.

Channel 4 is no stranger to programmes about sex. Recent output includes The Joy of Teen Sex, The Sex Education Show and last year's Sex Box, presented by Mariella Frostrup.

But Sex Box, which aimed to help Britain get over its sexual repression, was largely ridiculed. It featured couples having sex in a box in a television studio, then emerging in front of the cameras.

Separately, Channel 4 has also commissioned a second series of reality show The Island with Bear Grylls featuring two separate islands – one with men and one with women.

Humphreys said the original idea was a "social experiment about masculinity" but he wanted to move it on with the second series.

"These things need to evolve and become different, we didn't want to do the same experiment all over again," he said.

"It will still be a survival show but also we could turn it into more of a gender experiment. The two islands won't directly talk to each other, they will be standalone shows scheduled in the same week. People can watch both shows and make their own mind up."

Critics accused the Grylls show of misleading viewers but Humphreys said: "If you look at it under a microscope we were completely robust about it. It was a flash storm that actually helped the show, viewing figures went up the following week. We were delighted with the way it resonated with the public."

'Too biological, too inconsisent and too late'

Sex and relationship education (SRE) is too biological and taught at too late an age: by the time most young people receive it, they're past puberty. Learning about biology does not provide understanding about relationships, boundaries or consent, so young people are less able to negotiate these things. A class on STIs doesn't help them to feel comfortable about their sexuality, so they lack the language to express that.

The earlier SRE is taught, the better-equipped young people will be to have healthy relationships and fulfilling sex lives later on. Not teaching them these things is to rob them of the necessary life skills they deserve to have.

It may seem shocking to suggest 10-year-olds are taught about masturbation, but it's just another bodily function, which they should know about without shame or embarrassment. We need to help children to understand how their bodies work, in an age-appropriate way, not to enforce our own sexual repression. Teenagers complain that they are not given enough information about sex and relationships, and that this leaves them ill prepared.

I think a GCSE in sex education would be a great way to help young people to navigate all these things, and to assess whether they are learning about it properly or being taught it consistently. Just as doing an English GSCE helps young people to develop and practise judgment and critical thinking, so could one in SRE. It could prepare them for handling difficult issues in their own lives, and contribute to their emotional, physical and sexual wellbeing.

I sincerely hope this programme will start a change in sex education in this country, so that it becomes a mandatory subject, at appropriate ages, in primary and secondary schools. It's also great that Channel 4 will not just be highlighting the gaps in young people's SRE knowledge, but also shining a light on adult Brits' sexual repression. Sex shouldn't be clouded by 'Carry On-style embarrassment: adults and young people should be able to discuss it openly, without fear of judgment or worry about being stigmatised.

Perhaps this programme will enable us all to begin that conversation.

I'm not saying it won't be awkward at times, but we need to get beyond that and be able to talk about sex as the healthy, positive, natural thing that it is. Some people have sex. Get over it. Zoe Margolis

• Zoe Margolis is a writer and journalist who specialises in sex and gender issues. She is also an ambassador for the Brook Advisory Centre, which provides sexual health services and advice for people under 25.