Cross-country skiers Larissa Lazutina and Johann Muehlegg tested positive for the drug, which is not yet officially recognised as illegal but is very similar to the banned substance EPO.
"The publicity surrounding this substance was that we didn't have the detection methods," said Michele Verroken, the director of ethics and anti-doping at UK Sport.
"We certainly have a successful detection method"
"Now that the detection methods are finalised and considered by the scientific community as above legal challenge, it's a stark warning to athletes that you are taking a huge risk."
Darbepoetin is so new that it is only listed on the IOC anti-doping code by association with EPO.
It increases the level of haemoglobin - oxygen-carrying red blood cells - in the body, and so boosts endurance.
"It's reported to be ten times more powerful than EPO, which is the drug that most people would associate with an increase in red blood cells," Verroken told BBC Five Live.
"It would be extremely helpful to endurance athletes who want to get through the point when lactic acid affects their performance."
No legal challenge
Verroken admitted that there was concern over the ability to detect the use of darbepoetin in the lead up to the Games.
"It was actually a BBC journalist who discovered that this drug was quite easily obtainable over the internet.
"We were aware that a substance like this could potentially be used and there's always been concern about how we were going to identify the blood-boosting products.
"The testing process that we formulated for Sydney included a blood test and a urine test.
"The IOC have been able to take this process forward and have identified the substance.
"And if it's there and it cannot be legally challenged then we certainly have a successful detection method."
Despite the positive tests, Lazutina and Muehlegg retained the gold medals they won in earlier events at the Games.
"That leaves a slight dilemma," Verroken admitted.
"But the application of the IOC code would say it's only that performance that is considered, and you're removed from the Games.
"Any subsequent sanction from the ski federation might see all the performances nullified, but that would be a matter for later disciplinary action."
Another Russian, Olga Danilova, who finished eighth in Lazutina's event, was also disqualified for the same offence.