The broadcasting watchdog has dramatically tightened its grip on television programming, barring all talent shows from prime time and introducing extensive restrictions on popular American Idol-style contests. It may just be the latest move in a campaign aimed at 'purifying' television and stopping 'vulgarity', but some experts see it as part of a cleanup of the airwaves ahead of the Communist Party's 17th National Congress, which begins on October 15. A circular posted on the website of the State Administration of Radio, Film and Television on Thursday set out detailed rules for provincial television stations on talent shows, including a ban during prime time - 7.30pm to 10.30pm - from next month, and on viewers casting votes via telephones or the internet. Other rules cover everything from the length and design of the shows to what presenters, judges and participants can say and wear. Each provincial-level television station must apply for approval three months in advance if they plan to air a talent show on satellite networks. They must not air more than one talent show a year, which must not run for more than two months or 10 episodes. Each episode must not run more than 90 minutes. Only the final episode can be aired 'live', with a one-minute delay. People with low morals should not be on the shows. Participants must speak positively, and speak and dress in a way that corresponds to 'popular beauty standards'. Presenters must be socially responsible and must not make fun of, flirt with or praise each other. They must not be too intimate with judges or participants. Judges must be able to elevate the artistic standard of viewers and panels must be approved by the watchdog. Earlier moves included a blanket ban on radio and television programmes on sex and sex-related topics. But talent shows have been dealt the strongest blow so far. A Chongqing talent show was ordered off the air last month for being coarse and lacking taste. The station was reprimanded for allowing a 'chaotic live situation' where judges and participants could say what they wanted. 'A positive reading of the measures is that such talent shows have been promoting a belief in instant fame, which exerts a negative impact on teenagers,' Renmin University sociology professor Zhou Xiaozheng said. 'A negative reading is that it's part of a general hush-up before the 17th party congress. The authorities care little about [freedom of expression] now; the priority is to eliminate chances of things going wrong.'