The Trust ruled that comedian Frankie Boyle's remarks about the Olympic champion "risked offending the audience" and described his jokes as "humiliating". The original show, which was broadcast in August 2008, received 75 complaints.
Jokes about Adlington's appearance and sexual innuendo should not have been included by the show's producers, said the Trust's Editorial Standards Committee. It argued that Adlington had not courted celebrity status, making personal gags unjustified.
"The ribbing may have gone a tad too far on this occasion," one of the programme's producers told the BBC.
A similar complaint about a joke concerning the Queen was not upheld.
Scottish stand-up Boyle confirmed earlier this month that he is leaving Mock The Week to focus on other TV projects.