These findings in a poll of 2,300 high school students in the Xuanwu district of the capital have stunned teachers and Chinese sex experts.

Chinese society has traditionally venerated virtue, while under Communist Party rule since 1949 puritan abstinence has long been seen as proper behaviour. However, the survey shows a stunning shift in sexual mores.

Six per cent of students surveyed had already had a sexual experience and the average age for students to lose their virginity was 15. In 2005 a survey by Durex, the condom-maker, showed that the global average age was 17.3.

Just six of the 1,300 girls questioned stated that they would say no to sex when asked by a boyfriend. The typical answer was: “As long as he loves me, it’s OK.” About 200 respondents of both sexes said they would have a one-night stand if the opportunity arose.

About 30 per cent of the respondents said teenage sex was fine, as long as it was consensual, and 55 per cent said it depended on how much the two young people loved each other. There was no mention of moral considerations.

Such liberal attitudes have sparked concerns over safe sex, with more than 40 per cent of respondents who had had sex saying they did not use contraceptives during their first sexual encounter. Underage girls account for about a quarter of the 1.5 million abortions in China every year, and teenage pregnancies are on the rise.

Zhang Meimei, a professor at Capital Normal University in Beijing, who was involved in the latest survey, said: “The new generation is open-minded about sex. We can only conclude that it is a result of a fast-changing society.”

One of the most important changes is a result of China’s quarter-century-old “one-couple, one-child” family planning policy that has resulted in a generation of young people indulged by their parents and subject to little discipline and few rules at home.

In addition, the chaos of the Cultural Revolution shattered many traditional ways of thinking, while a widespread cynicism with communist ideology that followed the ultra-leftist movement has created a generation lacking a clear moral compass.

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