Adam Peaty has spoken of his concerns about losing to fellow swimmers who have previously been convicted of drug use.
Peaty, 20, won gold in the 50m and 100m breaststroke at the World Championships last week, as well as gold in the 4x100m mixed medley.
He was beaten to the award of male of swimmer of the meet by Sun Yang, who won gold in the 400m and 800m freestyle and silver in the 200m.
"People are sceptical about nations out there and whether they are clean," Peaty told BBC Sport. "All I can do is improve my times and hope I don't come second to someone who dopes."
Sun, 23, was banned by the Chinese Swimming Association last year for three months after testing positive for a banned stimulant.
"I don't know what's gone on behind the scenes," said Peaty. "But it's disappointing to see that he was let off so cautiously - it's like a slap on the wrists.
"It's not a good message - this is not [just] Sun Yang, it's doping as a whole. People out there now will be thinking 'if I can dope and not get caught then why am I doing it the hard way?'"
Six-time world champion Mark Foster recently backed Peaty to win gold at the Rio 2016 Olympic Games.
