The National Institute for Clinical Excellence (Nice) has underlined the importance of sex education for children and has said that it should be on the curriculum from primary school to early adulthood.
But family campaigners have slammed the plans for children as young as five to have sex education lessons, branding them 'unnecessary and harmful.'
They fear it could lead to teenage pregnancy being seen as acceptable.
"There is no evidence which shows that the more children are taught about sex, the less likely they are to become pregnant," the Daily Express quoted author and social policy expert Patricia Morgan as saying.
Morgan added: "The more children are told, the more likely they are to experiment."
According to draft guidance from health watchdog Nice, good teaching on sex will spread awareness and youngsters will be cautious.
"This guidance has made recommendations on effective teaching approaches, which include parents discussing school topics at home, and class visitors such as a teenage parent," said Gillian Leng, deputy chief executive of Nice.