Sun has yet to respond, but changed to the ANTA uniform on the podium for the 800 m freestyle championship on Monday. However, he covered himself in a Chinese national flag, as well as a sticker of the Chinese national flag covering the ANTA logo on his chest.

ANTA is the official uniform supplier for Team China, while rival Chinese brand 361° is Sun's personal sponsor and an official partner of the Games.

"For sports, it is very important to obey the rules－and that includes the associated business rules," sports industry expert Wang Qi wrote on Weibo.

"While the whole Chinese delegation is wearing the white-and-red uniform of ANTA, only Sun Yang chose a yellow outfit by 361°. It appears to be a violation of the rules."

ANTA also waded into the argument, releasing the following statement: "As the official partner of the Chinese delegation and the Chinese Olympic Committee, ANTA designed the uniform for Chinese athletes on the podium.

"We believe that the Chinese delegation should react fairly to the violation of regulations."

Neither the Chinese delegation nor 361° have responded.

The 361° logo is ubiquitous in Jakarta, with the company providing volunteers, officials, journalists and torchbearers with all manner of equipment including shoes, shirts and backpacks.

ANTA has been Team China's official partner at the Olympics and Asiads since 2009; Sun has been contracted to 361° since 2011.

He is not the first Chinese athlete to face such a dilemma.

At last year's Chinese National Games, basketball players Zhou Qi and Guo Ailun were ordered to cover up a sponsor's shirt they were wearing underneath their Liaoning team uniform as they were presented with their gold medals by CBA chairman Yao Ming.

Badminton megastar Lin Dan also faced a similar conflict of interest after signing an endorsement deal with a rival of team sponsor Li Ning.

The mini-furor in Indonesia, however, couldn't detract from Sun's stunning grand slam feat.

"I've waited eight years for this title," he said after clocking in at 1 min 45.43 sec, finishing just over a second faster than of silver medalist Katsuhiro Matsumoto of Japan.

"It's a perfect result, a dream come true,” Sun said. “It's unbelievable."