The International Olympics Committee (IOC) said critics of 16-year-old Chinese Olympic swim- mer Ye Shiwen, who took five seconds off her personal best and more than one second off the world record in the 400-metre individual medley, should "get real".
IOC communications director Mark Adams said: "These are the world's best athletes competing at the very highest level. We have seen all sorts of records broken already all over the place."
His comments came after US coach John Leonard described Ye's performance as disturbing and unbelievable.
However, Mr Adams said London 2012 has "a very, very strong drug-testing programme and we are very confident that, if there are cheats, we will catch them, as we already have done".
Asked if he was disappointed thoughts turned to doping whenever a world record was smashed, he added: "It is inevitably a sad result of the fact there are people who dope and who cheat.
"But I equally think it's very sad if we can't applaud a great performance. Let's always give the benefit of the doubt."
British Olympic Association chairman Lord Moynihan also hit out at those who had raised suspicions about Ye.
He said: "We know how on top of the game the World Anti-Doping Agency are and it has passed her as clean. That's the end of the story.
"It is regrettable there is so much speculation out there. I don't like it. I think it is wrong."
The comments were echoed by Mike Whittingham, director of High Performance at the Scottish Institute of Sport, who said he trusted the Olympic anti-doping procedures and believed athletes can make the sort of progress demonstrated by the 16-year-old if they have the right sort of preparation.
He said: "In this day and age, elite athletes can make massive steps forward through a combination of factors. The right athlete doing the right programme with the right coach – when you get these right, you can make fantastic progress."
In a final, the first five athletes are tested with two others, the IOC said. It said one athlete had been suspended and another given a temporary suspension as a result of the testing programme in the run-up to the Games.
Some 1706 tests have been carried out so far, the IOC added.
China's past record for its swimmers failing doping tests has led to the suspicions.
Her swim was described as "insanely fast" by previous world record holder Steph Rice. In the final 50m, Ye swam faster than the men's champion Ryan Lochte.
Mr Leonard, the executive director of the World Swimming Coaches' Association, said: "The one thing I will say is history in our sport will tell you every time we see something 'unbelievable', history shows us it turns out there was doping involved.
"That last 100m was reminiscent of some old East German swimmers, for people who have been around a while. It was reminiscent of 400m individual medley by a young Irish woman in Atlanta."
That was a reference to Irish swimmer Michelle Smith, who was banned for four years in 1998, two years after Atlanta, for tampering with a urine sample.
Mr Leonard said of Ye: "She looks like superwoman. Any time someone has looked like superwoman in the history of our sport they have later been found guilty of doping."
Ye said: "The Chinese team keep very firmly to the anti-doping policies, so there is absolutely no problem."