Britain's Olympic Greco-Roman wrestling medal hope Myroslav Dykun has failed a doping test.
The Ukrainian-born 29-year-old, who won 2010 Commonwealth gold for England, faces a two-year ban after a positive test for a banned recreational drug.
Dykun is suspended pending the outcome of a second test on the B sample, and a disciplinary hearing.
"Myroslav had the potential to do well [at London 2012]," British Wrestling chief Colin Nicholson told BBC Sport.
"The situation is extremely disappointing for the sport.
"We believe it's tested positive for amphetamines, which we see as recreational - not performance enhancing in the sport of wrestling.
"Under no circumstance can British Wrestling condone drugs in sport whether performance enhancing or recreational.
"British Wrestling will not tolerate such behaviour from anyone and we are supporting the drug testing programme.
"The fact we've got in effect an athlete caught is evidence we are determined to work in partnership to route out anyone misusing substances.
"British Wrestling will support the fastest resolution of this case."
UK Anti-Doping said in a statement that the "suspension follows a test conducted as part of the organisation's pre-Games testing programme in the countdown to the summer's Olympic and Paralympic Games".
Dykun, who married a former British wrestler, attained British citizenship more than five years ago as a result of length of residency in the country.
He did not attend the European Olympic qualification event in Bulgaria or the first World Olympic qualification event in China and upon the news of the positive doping test, was withdrawn from the squad for this week's second World Olympic qualification event in Helsinki, Finland.
Dykun is one of a number of Eastern European wrestlers who were brought to Britain to help develop a world-class academy in Manchester.
In 2007 Yana Stadnik and Olga Butkevych joined the set-up as sparring partners.
However, last year several British wrestlers alleged that roles had been reversed and GB athletes were now acting as training partners to their foreign counterparts who were eligible to compete for Britain.
Stadnik has been allowed to compete for Britain by the sport's international governing body (FILA) for the past few years on the understanding that she would be eligible for British citizenship in time for London 2012.
In March it was reported that she had failed in her bid for a passport in time for the Olympics, though British Wrestling says it has yet to hear "conclusive news" from the Home Office.
British Wrestling will have a selection panel meeting on 10 May and London 2012 competitor names need to by submitted to the British Olympic Association by 1 June.
Britain's last Olympic medal in the sport was in 1984 when Londoner Noel Loban won bronze in Los Angeles.