The Porsche Sun Yang drove. [Photo\ provided to China Daily]

Olympic swimming champion and world record holder Sun Yang has been given a seven-day administrative detention for driving without a license, after he was involved in a minor collision with a bus on Sunday.

The famous swimmer has also been temporarily banned from training and any commercial activities.

The sports star's arrest is embarrassing because he has been the public face in China of the Hyundai SantaFe SUV since December last year, appearing in television adverts for the vehicle despite admitting to not having a driving license.

The collision took place in Hangzhou, Zhejiang province, on Sunday, when the Porsche Cayenne SUV he was driving was hit from behind by a bus. The 21-year-old swimmer told police that he had borrowed the SUV from a relative, but had left his driving license at home, Youth Times reported.

However, police could find no record of Sun having a driving license, based on the ID number he provided, and he was arrested.

Sun rocketed to fame after becoming the first Chinese man to win two gold medals for swimming at the 2012 London Olympics, becoming one of the country's most sought-after sportsmen.

When he signed the endorsement deal for the Hyundai SantaFe SUV in December, he admitted in public that he had no driving license.

In the commercial, Sun stands beside the SUV and discusses its functions, but does not drive the vehicle.

"The commercial is beyond reproach, as long as it doesn't include any shots of him driving," said Yi Shenghua, an attorney at Yingke Law Firm in Beijing. "A star agreeing to be the spokesperson for a brand indicates that he or she loves the product."

However, many sports fans have expressed their disappointment on discovering that Sun has broken the law.

"I couldn't believe it was true until I saw the apology on his micro blog. It's like the Michael Phelps marijuana case all over again," said Xu Ming, a sports reporter for a Shanghai newspaper.

Sun, a native of Hangzhou, wrote on his micro blog account that as an athlete he should have been a role model and a public figure, but had failed his responsibility.