Just days after Australian swimmer Mack Horton stoked controversy by refusing to join a Chinese rival accused of doping on the podium, British freestyler Duncan Scott has refused to shake hands or pose for photos with Sun Yang.
In footage broadcast of the 200m freestyle medal ceremony in South Korea, Sun appeared to yell at Scott as the British swimmer walked behind him.
Sun was awarded the gold medal after Lithuanian Danas Rapsys was disqualified for a false start, while Scott came in third-place.
Unlike the 400m medal ceremony, in which Sun won his fourth-consecutive world title, Scott stood on the podium during the anthem but stepped aside afterwards to avoid photos with Sun as Chinese supporters booed.
In a statement on Tuesday, swimming's world governing body said Horton and Swimming Australia would receive a formal warning for the protest which received global attention.
"While FINA respects the principle of freedom of speech, it has to be conducted in the right context," FINA said.
China's Sun Yang, right, gestures to Britain's Duncan Scott following the medal ceremony in the men's 200m freestyle final. Source: AP
"As in all major sports organisations, our athletes and their entourages are aware of their responsibilities to respect FINA regulations and not use FINA events to make personal statements or gestures."
Following Horton's silver place in the 400m race, and his refusal to stand with Sun and shake his hand, he told reporters that he was "frustrated".
"I don't think I need to say anything," Horton said.
"His actions and how it has been handled speaks louder than anything I could say."
Sun, a 10-time world champion, was accused in 2018 of destroying vials of his blood that were due to be taken for drug testing.
The Chinese athlete, who had also served a three-month doping suspension in 2014, was not punished by FINA for smashing the vials because the drug testers did not show adequate identification.
The World Anti Doping Agency has appealed the finding, which could see Sun banned from the 2020 Olympics in Tokyo.
