A religious newspaper reported on Wednesday that Shaikh Muhammad Sayyid al-Tantawi, the head of al-Azhar institution, said sex education should be taught "in a way that doesn't stir instincts, or offend public morality".
According to Al-Liwa al-Islami, or The Islamic Banner, al-Tantawi said this was "better than teaching sex to school students and permitting the so-called safe abortion and calling for equality between man and woman through gender culture".
The comments come amid attempts to revive plans to revamp reproductive health education in schools.
Discussing issues related to sex is a taboo in conservative Egypt. Premarital sex and homosexual relations are considered a sin in Islam, the state's official religion.
Mahir al-Haddad, general director of al-Azhar's research centre, said al-Tantawi was responding to questions from non-government organisations whether sexual education was permitted.
Government ministries and civil groups in Egypt have been trying to find ways to teach reproductive health and HIV/Aids prevention without raising religious objections, particularly by treating it as an issue of health rather than sex.
"[Islamic teachings on sex] are better than teaching sex to school students and permitting the so-called safe abortion and calling for equality between man and woman through gender culture"
Muhammad Sayyid al-Tantawi,
head of al-Azhar institution
Suha Abd al-Qadir - an official at the government-affiliated National Centre for Childhood and Motherhood - said the term sex education might push clerics against the initiatives.
Reproductive health issues are already included in science classes, but some teachers simply do not teach them because they are shy, Abd al-Qadir said.
Al-Tantawi said Islam recognises only one way of making a family - through marriage between a man and a woman.
The Islamic cleric said this avoids the need to discuss issues of premarital sex, or the need to provide contraceptives to young people or the issue of abortion.
"It is their families that don't want them to know. The girls and boys wanted to know. They had a lot of questions"
Suha Abd al-Qadir,
Last month, Egypt's Grand Mufti Ali Gumaa rejected any courses that teach children safe sex and how to avoid pregnancy and disease on the grounds that they would promote sexual activity.
But Abd al-Qadir, whose centre has held seminars on reproductive health in high schools, said young girls and boys have a lot of appetite for knowledge about such issues.
"It is their families that don't want them to know," she said.
"The girls and boys wanted to know. They had a lot of questions."