World champion Tim Don has been given a three-month ban from triathlon after he missed three out-of-competition drugs tests in an 18-month period.
Don was crowned world champion in Lausanne last month
Don, who has passed nine tests on separate occasions this year, does not plan to appeal against the punishment.
British Triathlon chief executive Norman Brook said: "There is no suggestion that Tim Don was guilty of anything other than forgetfulness."
Don said: "I have never taken a performance-enhancing drug in my life."
Uk Sport's national anti-doping policy requires athletes to update an online database saying where they will be available for testing for one hour per day at least five days a week.
If they are not where they say they will be when a doping control officer arrives, the incident is reported as a missed test, three of which add up to an anti-doping rule violation.
UK Sport's head of operations for drug-free sport, Andy Parkinson, said: "It's disappointing that another British athlete has fallen foul of this particular rule, but the whereabouts system is a key element in the fight against doping in sport.
"It is essential that athletes understand their responsibilities and take the consequences of missing tests seriously."
Don added: "I fully understand that it is my responsibility as a professional athlete to log my whereabouts on the UK Sport system.
"I accept that it is due to my forgetfulness and lack of understanding of the online system following its launch last year that I have received this ban.
I will try to make the best of this situation to educate other athletes
"However I am a clean athlete and am totally aware of the importance of drug-testing and fully support the efforts made by UK Sport and British Triathlon to catch cheats.
"Instead of appealing I will try and make the best of this situation by using what has happened to me to educate other athletes."
The British Triathlon Association issued a statement in which they said they felt the testing system could be improved.
Don was found guilty by an independent disciplinary tribunal.
The BTA said in a statement: "The Tribunal also considered that there were inconsistencies and inadequacies in the existing system, giving rise to confusion which is not in the interests of athletes, the BTA or UK Sport."