At first glance, the new rules handed down by China's broadcasting authority seemed natural enough in a country where the Communist Party feels duty-bound to set the tone for everything, even pop music.

Masters of ceremony on state television's seemingly endless roster of variety shows, the regulations said, should avoid vulgarity, dress modestly and uplift their young viewers. "Hosts and hostesses represent the image of radio and TV stations and therefore have an unshakable responsibility to spread advanced culture and national virtue and to safeguard the country's interests," the authorities decreed.

But also in the latest set of rules, published Sept. 10 by the State Administration of Radio, Film and Television, was a less obvious stipulation: Masters of ceremony should always use standard Mandarin Chinese and should stop affecting Hong Kong or Taiwanese slang and accents.

To millions of Chinese, particularly boys and girls in the provinces who constitute the main audience for pop-oriented variety shows, Hong Kong and Taiwanese speech has come to mean being cool. The reason is simple. Most of the music and performers making teenage hearts throb here have long originated in the freer atmospheres of Hong Kong and Taiwan.

As a result, some hosts and hostesses of mainland variety shows have taken to throwing Taiwanese slang words and Hong Kong tones into their on-air speech, associating themselves with the cool radiating from those two centers of the Chinese-language pop industry. Saying "very pretty" with a drawn-out hao hao piaoliang ye as they do in Taiwan, for instance, has been branded more with it than the direct hen piaoliang of standard Mandarin.

But for nearly a year, the government broadcasting authority has been engaged in a purification project, designed to halt what officials feel is the creep of vulgarity and non-Chinese influences into programs offered by the country's 3,000 national, provincial, city and county stations. The campaign fits into a general tightening of government controls over broadcasting and other media, including additional Internet rules banning "unhealthy news stories that will mislead the public."

One producer at Beijing-based China Central Television said official expressions of concern have become so frequent that the latest set of regulations drew little attention within the profession. But one place they certainly drew notice, another specialist suggested, was in Hunan province's satellite television studios.

That official station this summer broadcast a groundbreaking singing contest in which viewers were asked to vote for their favorites by cell phone message, "American Idol"-style. The show, "Mongolian Cow Sour Yogurt Supergirl Contest," was such a hit across the country that state media estimated that 20 million people watched the final episode and that millions happily paid special fees to submit their votes via cell phone.

The show's several elimination rounds and its final episode drew more viewers than even China Central Television's highly rated Spring Festival spectaculars. Some commentators suggested that the success showed that people liked the power of the vote and maybe would like to choose their political leaders in the same way.

The phenomenal number of viewers meant that advertising rates soared, beyond what China Central Television charges for spots on its most popular programs. The main sponsor, Mongolian Cow Dairy, went from third-largest to the largest dairy in the country during the show's run. Sales more than doubled, according to the Shanghai Daily newspaper. The China Europe International Business School announced that it would make the "Supergirl" show a case study for its master of business administration program.

Worst of all to the Beijing officials who direct China's broadcasting, the show was emceed by Li Xiang, an edgy pop music hostess from the provinces who is well known for using Hong Kong and Taiwanese words as she banters with singing stars onstage. And the winner was a spike-haired, punky-looking Sichuan province student, Li Yuchun, who deviated so clearly from the standard of soft beauty espoused by China Central Television that bloggers described her as "boyish."

The new rules were issued a week after the finale and included a mention that "flirtatious and affected manners on stage" are also banned. Nevertheless, Li Yuchun announced plans to record an album and has scheduled promotional appearances across the country, including at the prestigious Peking University.

Yu Dan, director of a mass communications institute at Beijing Normal University, said the use of Taiwanese and Hong Kong phrases actually went out of fashion several years ago in big-city studios such as those in Beijing or Shanghai. A China Central Television producer agreed, saying the rage now is getting out of the studio to make audience participation programs in which the master of ceremonies is less important.

"But 70 percent of Chinese television stations are at the city or county level, and they don't have the money, the vision or the human resources to move forward," Yu said. "So their programs are stuck in the last century. They don't know how to renew their offerings."

The State Administration of Radio, Film and Television declined to comment on the new regulations, saying they were suggested by the equally official China Radio and Television Society, an association of industry workers. At the society, a spokeswoman queried by telephone and fax said officials were unable to provide an immediate comment but were working on one.

Winner Li Yuchun, center, Zhou Bichang, left, and Zhang Liangying in the "Supergirl" singing contest.