The future use of genetic technology by athletes to re-engineer their bodies will be detectable, MPs have heard.
Doping testers are ahead of gene-dopers, an expert says
Arne Ljungqvist, of the International Olympic Committee, said it was widely thought so-called "gene doping", which is illegal, was impossible to pick up.
But experts were "a little ahead of those who may be tempted to use that method for the purpose of doping", he told the Commons science committee.
Chairman Phil Willis said he had "never heard" that gene-doping was detectable.
It is feared athletes could use the technique to gain advantages such as greater endurance or bigger muscles.
They would be able to create a gene mutation through a single injection, without leaving substance traces, unlike the misuse of drugs such as anabolic steroids.
But gene doping could damage their future health.
Professor Ljungqvist, chairman of the IOC's medical commission, said it was impossible to establish if cheats had already used the method, but insisted it would be possible.
He added: "We are a little ahead of those who may be tempted to use that method for the purpose of doping.
"So by the time that gene doping is there we hope and believe that we will have a method to detect it."
Mr Willis asked Professor Ljungqvist to send the committee evidence to back up his "powerful" statement.
"It's something we've never heard anywhere else," he said.
Prof Ljungqvist also said some "educated" athletes were taking existing illegal drugs, as they "weren't thinking about" the health risks.
Richard Budgett, chief medical officer of the British Olympic Association, said 2.13% of sportsmen tested were found to have traces of banned substances.
He said doping bans "should be four years, particularly in Olympic sports", where competitors had to reach their peak once every four years.
Athletes in some sports "justified [drug use] to themselves... by saying 'I'm just levelling the playing field", he added.
Dr Budgett said: "In my own sport of rowing there's a low prevalence, whereas in some other sports like cycling there are more cases.
"I think it's probably the events and the culture of the sport."
He added: "The financial side is important because there is a lot of money in professional cycling and the stakes are higher and that will drive people to cheat."
Prof Ljungqvist said use of anabolic steroids and other performance-enhancers was also more common among amateur sportsmen than top athletes, as they were far less likely to be tested.
The IOC had set up its fight against doping after a cyclist died in the Rome Olympics of 1960, Prof Ljungqvist added.