Ye Shiwen calmly takes another gold as drug claim storm rages around her

The teenage Chinese swimmer at the centre of a global controversy over allegations of doping accused her critics of being biased against Chinese athletes just hours after winning a second gold medal in Olympic record time.

"In other countries, other swimmers have won multiple golds and nobody has said anything," Ye Shiwen told a news conference following her victory in the 200m individual medley at the Aquatics Centre. "How come people criticise me just because I have won multiple golds?"

Asked directly if she had ever used performance enhancing substances, the 16-year-old said: "Absolutely not." Her own success and that of other young swimmers such as 17-year-old US athlete Missy Franklin was "because of our training, because we work really hard," she said.

The swimmer found herself at the centre of an international doping storm following her victory in the 400m individual medley on Saturday, during which she swam a final freestyle leg of such remarkable acceleration that she overhauled the race leader and finished almost three metres ahead of her, in world record time. She swam the final 50m of the race faster than the American swimmer Ryan Lochte in the men's race.

On Monday, the leading US coach John Leonard, executive director of the World Swimming Coaches Association, questioned the performance, telling the Guardian: "We want to be very careful about calling it doping, [but] the one thing I will say is that history in our sport will tell you that every time we see something – and I will put quotation marks around this – 'unbelievable', history shows us that it turns out later on there was doping involved."

His comments provoked an angry response from China's head of doping control, Jiang Zhixue, who called the remarks "not proper" and said: "Some people are just biased. We never questioned Michael Phelps when he bagged eight gold medals in Beijing."

The swimmer's father, Ye Qingsong, stepped into the fray, telling the Chinese news portal Tencent that while it was "normal" for people to be suspicious, "the western media has always been arrogant and suspicious of Chinese people".

Others also defended the teenager, pointing out that there was no evidence she had used illegal performance-enhancing substances. An IOC spokesman, Mark Adams, said: "These are the world's best athletes competing at the highest level. We have a very, very strong drugs testing programme. If there are cheats we will catch them."

Speculation about doping, he said, was "a sad result of the fact that there are people who cheat. If you cannot applaud a good performance, let's give the benefit of the doubt."

Colin Moynihan, chairman of the British Olympic Association said: "She's been through Wada's [the World Anti-Doping Agency] programme and she's clean. That's the end of the story. Ye Shiwen deserves recognition for her talent. Let's recognise an extraordinary swimmer."

Ye, the world champion, said Leonard's suggestions were "unfair", but said they hadn't affected her. "I want to thank my coaches, and also my teammates and parents," she said. "They have been supporting me a lot. They are the people who can make me strong and that's why I'm not that affected by outside noise. I also feel they [those criticising her] are biased."