Amir Khan is flabbergasted by the revelation that he may now have to spend the rest of his years branded as a drug cheat.

The now retired former unified junior welterweight champion from Bolton, England, is concerned his legacy could be ruined for good after it was revealed Tuesday that United Kingdom Anti-Doping slapped him with a backdated two-year ban stemming from a positive drug test administered shortly after his stoppage loss to rival Kell Brook on February 19.

The test revealed traces of ostarine, an anabolic agent.

An Olympic silver medalist, Khan was one of the biggest names in British boxing for the past decade-and-a-half.

Khan did not dispute the UKAD results, but he maintained nonetheless that did not intentionally ingest the substance in question. The UKAD inquiry ruled out the possibility that Khan knowingly and deliberately took the substance and concluded that the amount found in Khan’s body was too minuscule for Khan to reap any sort of benefit.

“I have no idea [how the substance entered my body],” Khan told Sky Sports. “It could be meeting people, shaking people’s hands. The amount of ostarine in my blood was 0.5, which is say [in] an Olympic size swimming pool, it's smaller than a grain of salt.

“I don't know how it got into my system, maybe shaking hands, maybe sharing a drink with somebody.”

Khan added, “The results say it could not have changed my performance and with the amount that was in my blood it could not have made me any stronger or better. It was such a tiny amount which somehow got into the system.”

Khan made it clear he is now worried his legacy could be forever tarnished. Khan retired after his bout with Brook.

“I don't want to be remembered for something like this, that'll hurt me a lot,” Khan said. “If people remember me for just this incident that's happened then I think it'll always upset me because I know it was never done on purpose.

“Hopefully people believe me and maybe take more precaution, especially the young and upcoming fighters can learn from me how mistakes can happen.”

“I'm very sorry. I have to take some sort of responsibility,” added Khan, who said he will personally reach out to Brook and “clear” matters up.

News of Khan’s positive drug test follows in the wake up of one of the biggest scandals in British boxing from last year: welterweight Conor Benn's two separate positive drug tests.

Unlike Khan, Benn has repeatedly maintained his innocence and has suggested that laboratory contamination is to be blamed. Benn is still under investigation by the British Boxing Board of Control.