England's Commonwealth 400m champion Christine Ohuruogu has been given a one-year ban for missing three out-of-competition drug tests.
Ohuruogu is now pondering her future
The British Olympic Association may now also ban her from competing at future Olympic Games for Great Britain.
Ohuruogu said: "I am utterly devastated and completely heartbroken by the decision to exclude me from competing."
She added she would now "be forced to rationally consider my athletics future in light of today's decision".
The independent disciplinary committee which heard her case released a statement saying that Ohuruogu "had no intention of infringing the anti-doping rules".
It said: "This is undoubtedly a very harsh sanction for the minor degree of fault attributed to a young athlete."
But John Scott, UK Sport's director of drug-free sport, defended Ohuruogu's punishment.
He said: "The sanction is in line with that set out within the IAAF's rules and reflects the seriousness of the offence.
"It sends out a strong signal to all athletes that making themselves available for testing is a key requirement on them, and they must ensure they deliver on their responsibilities.
"In many ways, this case has already proved to be a much needed wake-up call for athletes across all sports."
Ohuruogu, given a provisional ban by UK Athletics in August, faced a the independent hearing on Monday.
UK Athletics' chief executive David Moorcroft said: "For any anti-doping rule violation, UK Athletics appoints an independent disciplinary committee to consider the facts of the case in the context of the rules of our sport.
"We operate within a very stringent regime and accept the decision the independent disciplinary committee has made."
The International Association of Athletics Federations' rules on drug testing demand that all athletes alert the testers to their whereabouts for one hour a day, five days a week.
A ban for Ohuruogu, who is based just one mile from the site of the 2012 Olympics in East London, is a major setback to British medal hopes over the next few years.
She has the right to appeal to the British Olympic Association, and could also take the case to the international Court for Arbitration in Sport.
Ohuruogu's first missed test was on 12 October last year, with the final no-show coming just before last month's European Championships.
She blamed the vital third missed test on a change to her training schedule.
Katharine Merry, who won Olympic bronze in the 400m in 2000, fears Ohuruogu will now turn her back on athletics.
"It's very upsetting for her and I just hope that we keep Christine in the sport," she told BBC Five Live.
"She's an extremely book-smart girl and my fear is that we lose her to the sport totally because of this, which I hope will not be the case."