A nine-year-old Chinese girl's stunning performance at the Beijing Olympics opening ceremony has been marred by revelations she was lip-synching.

Lin Miaoke was lip-synching Friday to a version of "Ode to the Motherland" sung by seven-year-old Yang Peiyi, who was deemed not pretty enough to perform as China's representative.

The revelation on Tuesday came after it was also revealed that a spectacular pyrotechnics display of footprints making their way across Beijing was digitally inserted into television coverage of the event. It was presented as live coverage at the time.

CTV's Lisa LaFlamme, reporting from Beijing, said many Chinese feel dismayed and betrayed that the adorable girl who became an instant symbol of China's bright future, wasn't actually singing at the opening ceremony.

However, she said some Chinese don't fault officials for taking extreme efforts to make the ceremony perfect.

"We did hear both sides today but I would say the average person on the street is horrified at the notion that anything was faked," LaFlamme told CTV Newsnet.

The music director for the opening ceremonies, Chen Qigang, told Beijing Radio a last-minute decision was made to match Miaoke's face with Peiyi's voice.

"The director said the organizers' plan was for the seven-year-old to sing, but during rehearsals Chinese leaders ... decided the seven-year-old didn't fit the national image," said CTV's Steve Chao, also in Beijing.

"According to the music director the opening ceremony was so important to Chinese leaders, it was supposed to present a flawless image of the country to the rest of the world, and the seven-year-old didn't seem to fit the bill."

Though her voice was beautiful, Peiyi reportedly had some crooked teeth and didn't pass the cuteness test.

"The national interest requires that the girl should have good looks and a good grasp of the song and look good on screen," Chen, the music director, told Beijing Radio.

"Lin Miaoke was the best in this. And Yang Peiyi's voice was the most outstanding."

It is not clear whether Miaoke knew she was lip-synching.

A news story posted on the China News Service says a China Central Television reporter asked Peiyi whether she felt regret over the opening ceremony.

The little girl replied that just having her voice used for the opening ceremony was an honour.

Peiyi is a first grade student at a primary school linked to Peking University and has been described by her tutor as cute, well behaved and with a love of Peking opera.

Miaoke had appeared in a pre-Olympic commercial last year with hurdling champion Liu Xiang, and was already a celebrity in China.