A seven-year-old Chinese girl was not good-looking enough for the Olympics opening ceremony, so another little girl with a pixie smile lip-synched 'Ode to the Motherland,' a ceremony official said - the latest example of the lengths Beijing took for a perfect start to the Summer Games.

A member of China's Politburo asked for the last-minute change to match one girl's face with another's voice, the ceremony's chief music director, Chen Qigang, said in an interview with Beijing Radio.

"The audience will understand that it's in the national interest," Chen said in a video of the interview posted online Sunday night.

The news follows reports that some footage of the fireworks exploding across China's capital during the ceremony was digitally inserted into television coverage, apparently over concerns that not all of the 29 blasts could be captured on camera.

China has been eager to present a flawless Olympics image to the world, shooing migrant workers and so-called petitioners who come to the central government with grievances from the city and shutting down any sign of protest.

The country's quest for perfection apparently includes its children.

Lin Miaoke's performance on Friday night, like the ceremony itself, was an immediate hit. "Nine-year-old Lin Miaoke becomes instant star with patriotic song," the China Daily newspaper headline said today.

But the real voice behind the tiny, pigtailed girl in the red dress who wowed 91,000 spectators at the National Stadium on the opening night really belonged to seven-year-old Yang Peiyi. Her looks apparently failed the cuteness test with officials organising the ceremony, but Chen said her voice was judged the most beautiful.

"The national interest requires that the girl should have good looks and a good grasp of the song and look good on screen," Chen said. "Lin Miaoke was the best in this. And Yang Peiyi's voice was the most outstanding."

During a live rehearsal soon before the ceremony, the Politburo member said Miaoke's voice "must change," Chen said in the radio interview. He didn't name the official.

So Peiyi's voice was matched with Miaoke's face.

"We had to make that choice. It was fair both for Lin Miaoke and Yang Peiyi," Chen told Beijing Radio. "We combined the perfect voice and the perfect performance."

Chen couldn't be reached for comment today.

A photo of Peiyi posted today on popular website Sina.com shows a smiling girl with a fringe and crooked teeth. A China News Service story posted with the photo says a China Central Television reporter asked Peiyi whether she felt regret over the opening ceremony.

Peiyi responded that just having her voice used for the opening ceremony was an honour.

Whether the move was unethical, or unfair to both girls, has become a hot topic among Chinese and is racing across the country's blogosphere.

"The organisers really messed up on this one," said Luo Shaoyang, 34, a retail worker in Beijing.

"This is like a voice-over for a cartoon character," Luo said. "Why couldn't they pick a kid who is both cute and a good singer? This damages the reputation of both kids for their future, especially the one lip-synching. Now everyone knows she's a fraud. Who cares if she's cute?"

Zhang Xinyi, 22, who works in marketing in Beijing, disagreed.

"I can understand why they picked the prettier girl. They need to maintain a certain aesthetic beauty during the opening ceremonies. This situation is not so bad, especially since it gives two people an opportunity to shine rather than just one."

Peiyi is a first-grader at the primary school affiliated to Peking University. Her tutor, Wang Liping, wrote in her blog that Peiyi is both cute and well-behaved, with a love for Peking opera.

"She doesn't like to show off. She's easygoing," Wang wrote. She and other school officials couldn't be reached today.

Miaoke, however, was a minor celebrity even before the opening ceremony. The third-grader appeared in a television ad last year with China's biggest gold medal hope, hurdling champion Liu Xiang, and she was in an Olympics ad just before Chinese New Year, China Daily reported.

Miaoke has her own blog, and one of the latest photos posted since the ceremony shows her looking up nervously at the ceremony's director, film director Zhang Yimou. "Giving the child encouragement," the caption says.

Her father, Lin Hui, told China Daily he learned Miaoke would be "singing" only 15 minutes before the opening ceremony began. The newspaper wrote Lin "still cannot believe his daughter has become an international singing sensation."

It was the second straight Olympics where the opening ceremony involved lip-synching.

Luciano Pavarotti's performance at the 2006 Winter Games in Turin was prerecorded. The maestro who conducted the aria, Leone Magiera, said earlier this year that the bitter cold made a live performance impossible for Pavarotti, who was in severe pain months before his cancer diagnosis. Pavarotti died in September 2007 at age 71.