Usain Bolt says Tyson Gay should have been "kicked out" of athletics after being found guilty of using a banned substance in 2013.
Gay's ban was reduced after he agreed to co-operate with authorities -- a decision Bolt describes as "the stupidest thing I've ever heard" -- and the American sprinter is now set to return to action.
Speaking to Runner's World magazine, six-time Olympic champion Bolt said: "I was really upset about that. He got a year just because he talked to the authorities about how it was done and who helped him.
"That sends the wrong message. 'If you do it and get caught, just tell us all you know and we'll lower your ban'.
"It's the stupidest thing I've ever heard. The message should be: If you cheat you're going to be kicked out of the sport."
Bolt said he used to regard Gay, the joint-second fastest man in the world, as a rival but will no longer enjoy competing against the American.
"I'm not worried about him beating me," Bolt, who runs for Jamaica, said. "I think it's because I respected him so much over the years. He was a competitor, kept me on my toes and he pushed me to always do my best.
"Then to find out that he was on drugs -- it's a bit like I think parents must feel when they have a kid who does something bad and lets them down. I feel like he let me down and he let the sport down.
"It really bothers me."