South Africa captain Faf du Plessis has lost his appeal against a ball-tampering conviction, but will be free to play in the first Test against Sri Lanka starting on Boxing Day, Reuters reported.

Du Plessis was found guilty by match referee Andy Pycroft of changing the condition of the ball after appearing to use saliva tainted by a mint in his mouth to shine it during the second test against Australia in Hobart last month.

South Africa won the test and the series 2-1, but the victory was overshadowed by what Du Plessis felt was an unjust targeting of him.

The skipper was fined his entire match fee and had three demerit points added to his record, Reuters said.

If a player accumulates four-to-seven demerit points within a two-year period they are converted into two suspension points, which brings a ban for one test or two one-day internationals or Twenty20s.

Du Plessis appealed against his punishment on Monday, questioning whether his actions changed the condition of the ball at all.

The Chair of the ICC's Code of Conduct Commission, Michael Beloff, upheld the verdict, but stopped short of increasing the sanction to an automatic one-match ban which would have been within his remit.

International Cricket Council (ICC) chief executive officer Dave Richardson welcomed the decision.

"Although it was not picked up by the umpires at the time, when the incident came to our attention subsequently, we felt it was our responsibility to lay a charge in this case because the ICC can't let such an obvious breach of this Law pass without taking any action.

"We are pleased that both the match referee and Mr Beloff QC have agreed with our interpretation of the Laws and hope that this serves as a deterrent to all players not to engage in this sort of unfair practice in the future."

Du Plessis, 32, was last week confirmed as South Africa's new permanent captain after AB de Villiers resigned having missed three test series in a row due to an elbow injury.