In the wake of a Chinese doping scandal, Michael Phelps doubled down Monday on his support for tougher sanctions — including a lifetime ban for anyone who tests positive for a banned substance, according to AP.

“If you test positive, you should never be allowed to come back and compete again, cut and dry,” Phelps said. “I believe one and done.”

The World Anti-Doping Agency and World Aquatics have acknowledged that 23 Chinese swimmers tested positive for a banned substance ahead of the Tokyo Olympics. The results were not made public until media reports surfaced this year, with both bodies accepting the Chinese explanation that the positive tests were caused by tainted food.

Nine of those swimmers won medals - several as part of relay teams - in Paris, leading British star Adam Peaty to gripe that the playing field was not even.

Phelps reiterated those sentiments, saying the Chinese swimmers who tested positive should not have been allowed to compete in either Tokyo or Paris.

Or anywhere else, for that matter.

“If everybody is not going through that same testing, I have a serious problem because it means the level of sport is not fair and it’s not even,” he said. “If you’re taking that risk, then you don’t belong in here.”

When Phelps was setting multiple world records and becoming the most decorated Olympian ever, he knew there were plenty of people who scrutinized his performances, who wondered if he could be pulling off such amazing feats without a pharmaceutical boost.

Phelps said he actually subjected himself to extra testing in the leadup to the 2008 Beijing Olympics —where he broke Mark Spitz’s iconic record with eight gold medals — to alleviate any doubts he was racing clean.

Since retiring from the sport after the 2016 Rio de Janeiro Games, Phelps became more outspoken about issues such as mental health and anti-doping efforts. He recently testified before the U.S. Congress on the latter issue, calling for major reforms to a system that many people believe is broken.

“What has to happen is everybody has to come together and figure out one way to test everybody all over the world. Period,” Phelps said. “And if you test positive, you should never be allowed to come back and compete again.”