Bernard Tomic has been urged to apologise over his use of the word "retard" in a post-match news conference at Wimbledon.
Tomic overcame Fernando Verdasco 4-6 6-3 6-3 3-6 6-4 in a hard-fought first-round display at the All England Club on Wednesday.
However the 23-year-old Australian was forced to wait on court for several minutes before Verdasco appeared prior to the match.
When asked by a reporter about the wait, Tomic replied: "Yeah, I did get to the court prior to him very early, and unfortunately I had to stand on court like a retard."
The comments immediately drew criticism from Ciara Lawrence, who has a learning disability and is a campaigns support officer at Mencap.
"I'd like the player to apologise and would encourage him to meet people with a learning disability so he can understand why the word is so damaging and offensive," she is quoted as saying by the Daily Mail.
"Time and time again I hear this word used as if it has no effect. People clearly don't understand how upsetting and offensive this is to people with a learning disability like me.
"I am sick and tired of people in high-profile positions who are respected by the public using this word. It can make the public and people who look up to sports stars think it is OK to use words like this when it's not.
"It makes people with a learning disability seen not as people but as second-class citizens. It is no different to discriminating against someone who is gay or black."