Parentline Plus cautioned that the absence of guidance from fathers, especially for boys, might be contributing to the problem of teenage pregnancies in Britain, and the rise of sexually transmitted diseases among young people.
According to the organization, calls to its free helpline over the last few years showed that fathers often left it up to mothers or schools to hold difficult conversations with their sons and daughters.
The research revealed that most father were afraid that telling their children about the facts of life could ruin the time they spent together in the evenings or at weekends. The problem was more severe among divorced or separated fathers, who often have only a few hours each week or fortnight with their children.
The helpline, which takes over 100,000 calls a year, revealed that fathers considered it better to avoid dealing with tricky subjects that could lead to defensiveness or an argument.
The organisation will launch a campaign this week to persuade reluctant fathers to fulfil their responsibilities, and to help reduce teen pregnancies.
The campaign will suggest that fathers can educate their children about sex by holding a discussion on popular television shows or stories about celebrities. It will also recommend that fathers keep the conversation light-hearted, and tell their children funny stories about the time when they were teenagers in between.
"We know from other research that teenagers who talk to their parents about sex are more likely to delay having intercourse, have fewer partners and are more likely to use contraception. We need to engage fathers more in this process, encourage them to talk to their children and not just assume it is a mother's responsibility because she sees more of them," Times Online quoted Sue Ormesher, spokeswoman for Parentline Plus, as saying.
"There is an assumption that it is only important to talk to girls about sex because they are the ones who get pregnant. But it is just as important to talk to boys, to tell them about their responsibilities and encourage them to behave in a responsible way," she said, suggesting that fathers could be particularly effective in talking to their sons.