Children as young as five are being shown "explicit" images to teach them about sex, an evangelical Christian pressure group has claimed. The Christian Institute has complained that at least 10 books or teaching packs used in English primary schools for lessons on sex and relationships, contain images or descriptions that are "obviously unsuitable". Its report, Too Much, Too Young, criticises, among others, a BBC teaching pack for its images of a nude man and woman and the children's book Mummy Laid an Egg, by Babette Cole, for its child-like drawings of a man and woman having sex on a skateboard and wearing red noses. The book won British Illustrated Children's Book of the Year. A number of councils have recommended the books and lesson plans to schools in their area. The institute said many parents would be "deeply upset" to find these images were being shown to their children. Other teaching packs criticised in the report contain short explanations of bisexuality, anal intercourse and oral sex. The report suggests parents stand as governors at their local primary school so they have influence over which images pupils are shown. It recommends they ask teachers to show them the materials being used and, if they refuse, advises them to demand it through freedom of information legislation. "The current approach to sex education, which demands ever more explicit sex education at ever younger ages, has wasted hundreds of millions of taxpayers' money and comprehensively failed to reduce teenage pregnancy and abortion rates," said Mike Judge, head of communications at the institute. The Department for Education is conducting an internal review of personal, social, health and economic education, which covers sex and relationships. This will be published later this year. Currently, all primary schools are required to give lessons on human biology as part of the science curriculum. While lessons about sex are not compulsory, many schools choose to include them in the curriculum. Governors decide what is taught beyond the compulsory curriculum and parents are allowed to withdraw their children from any sex education lesson that is outside the science curriculum. The Sex Education Forum, which campaigns for all pupils to have high quality lessons about sex and relationships, said primary schools tended to teach children basic facts about the difference between boys and girls' bodies, and which parts of the body were private and should not be touched by others. "This is not about teaching primary school children to have sex. One of the purposes of sex and relationship education is to try to protect children from abuse," said Lucy Emmerson, principal officer at the Sex Education Forum. Teaching about sex and relationships was "patchy" in many schools and often "too little, too late", she added. "It is not acceptable for a child to finish primary school and not know what periods are or what they should do if they are abused." She said the images contained in books and teaching packs had to be seen in the context of a lesson rather than on their own. "We strongly advise parents to become involved in a school's decision on which teaching resources to use when teaching about sex," she said.