An Australian mentor of Chinese swimming sensation Ye Shiwen has slammed claims her Olympic achievements were fuelled by drugs, saying he was "100 percent certain" the teenager was clean.
The 16-year-old's explosive win in the Olympic 400m medley in world record time drew allegations of doping from John Leonard, executive director of the World Swimming Coaches' Association.
His suspicions were raised after her astonishing final lap was faster than US winner Ryan Lochte and Michael Phelps in the men's competition. Ye knocked five seconds off her own personal best time and has since added the 200m medley gold.
But Denis Cotterell, the former coach of Australian Olympic gold medallist Grant Hackett, has trained Ye and other top Chinese swimmers and said he was "100 percent certain" the youngster was clean.
"You have to have a look at the improvements in Beijing," he told the Australian Broadcasting Corporation of Chinese swimmers. It is a combination of their talent and their work ethic."
Cotterell said Ye's five-second improvement was not a one-off, pointing to Ian Thorpe and Michael Phelps as swimmers who also excelled early.
"(There have) been great achievements by people in the sport, it's part of the history ... And talent comes along and makes a good drop and shocks a few people but we generally seem to have accepted it," he said.
"But for some reason in this case now, it's not, because of the Chinese (history of drug use). Ian Thorpe, no one questioned. Michael Phelps, no one questioned," he added.
"And having worked with the girl and seeing how hard she works and the talent she is, it is disappointing that the kid is in the media conference on her own with 100 journalists having to defend herself."
Swimming's world governing body FINA has insisted there was "no factual basis" for speculation Ye's medley double was aided by banned drugs and she has also won support from numerous pool greats.