Official figures show that Japanese schoolchildren are having more sex than ever before, and that many are shunning condoms, unaware of the risks of contracting HIV and other sexually transmitted diseases.

　　Japan, which has an estimated 10,000 people living with HIV/Aids, is the only G7 country in which new cases of the virus have increased since 1993. A record 1,165 new cases were diagnosed last year, the health and welfare ministry said, with about 40% of all newly infected people in their teens or 20s.

　　Increased sexual activity among the young has been accompanied by a rise in other sexually transmitted diseases. One recent survey identified a disturbing rise in incidences of chlamydia among Japanese teenagers.

　　The number of teens diagnosed with the disease, which can cause infertility, rose to 6,163 in 2003 from 3,639 four years earlier, according to the health ministry. The actual figure may be even higher.

　　The trend has prompted a debate about the effectiveness of sex education in Japanese schools as teenage pregnancies rise to record levels.

　　While many parents and conservative politicians are appalled by graphic images in some sex education textbooks, health experts say teachers need to offer even franker explanations of the risks of unprotected sex.

　　A recent survey found nearly 40% of senior high school students aged 15 to 18 have had sex. Nearly half of 17-year-old girls have had sex, compared with 17% in 1990.

　　Experts blame a combination of a cultural reluctance to openly discuss sex in the home and a popular culture that often treats teenage girls as sex objects. In addition, the proliferation of online dating sites has led to a rise in enjo-kosai ("compensated dating"), a euphemism for teen prostitution, in which girls sleep with men they meet in chatrooms in exchange for cash or gifts.