Celtic winger Aleksandar Tonev has lost his appeal against a seven-match ban for using racist language.
A Scottish Football Association appeal tribunal threw out the appeal after the on-loan Aston Villa winger was earlier banned over an incident involving Aberdeen full-back Shay Logan.
The SFA has published the report of both panels who examined the case.
Celtic manager Ronny Deila had earlier indicated the club would challenge the decision further if it was upheld.
The appeal panel's verdict in full
The report of the original panel hearing stated that Logan had accused Tonev of saying: "Don't touch me you black c***" when the Aberdeen defender put his arm across the Celtic player moments after fouling him.
Tonev denied saying the offensive words and no-one else heard them but the panel heard that Logan quickly told his captain, Mark Reynolds, referee Bobby Madden, and manager Derek McInnes.
The report described Logan as an "impressive witness".
It added: "He gave his evidence in a careful and measured manner. He gave clear and unequivocal evidence that Mr Tonev had used the language complained of and that it had been targeted at him."
However, the panel stated they were unable to accept the Bulgarian as "either credible or reliable" on the central issue of the case.
The report continued: "His evidence on his understanding of the language said to have been used, was particularly unsatisfactory.
"In chief examination his evidence was to the effect that he did not know what the word 'c***' meant.
"On cross examination he explained that he had heard the term in his time at Aston Villa but did not know what it meant. He then accepted that he was aware that it was a term of abuse.
"The impression was of a witness giving a less than a full account of his actual understanding; and seemed to the tribunal to be an inherently improbable account."
Celtic, who were earlier issued with a UEFA charge over alleged "crowd disturbances" during their Europa League defeat by Dinamo Zagreb last week, said they were "extremely disappointed" by the outcome and vowed to take up the case with the governing body.
A club statement read: "We do not consider that any player should be found guilty of such a grave offence on the basis of the evidence presented in this case.
"Celtic Football Club will be approaching the Scottish FA to seek to address this issue.
"We would like to make it clear that at no stage was it ever suggested that Shay Logan had made any false allegations. However, Aleksandar Tonev's position consistently has been that he did not say the words that were alleged to have been said and that he is not a racist.
"Celtic Football Club has enjoyed an excellent relationship with Aberdeen Football Club and this, of course, will continue.
"As we have said many times before, racism has no place in football and as a club which has been open to all ever since its formation in 1888, Celtic abhors racism of any kind.
"Clearly, Aleksandar continues to have our full support."
Celtic will face another disciplinary hearing on February 19 when UEFA's control, ethics and disciplinary body meets to discuss the incident in Croatia, which saw a flare lit in the visiting end.
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