Gervais has frequently used the term since returning to Twitter, while also posting pictures of himself gurning for close-up camera shots.
Despite the use of the unusual pictures, Gervais has insisted that "mong" no longer had a connection to its original meaning, a derogatory term for people with Down's Syndrome.
"The word mong means Down's Syndrome about as much as the word gay means happy," said Gervais.
Comic and writer Richard Herring was one of the first people to question Gervais's attitude to the subject in a blog post earlier this week. The debate about the word has continued in various blogs and Gervais's Twitter followers have mocked Herring for his critique.
Gervais has told his fans on Twitter and his blog that a large amount of criticism of him has come from jealous comedy acts. However, his detractors have pointed out that the debate and Gervais's return to Twitter has coincided with the start of his new BBC Two series Life's Too Short.
Nicola Clark, a disability rights campaigner, wrote in The Guardian: "If a word referencing disability is applied to mean something ugly, foolish, unpleasant or weird, then it is an abusive epithet promoting a stereotype.
"Reclaiming a word to lessen its power is a right only available to those to whom the abuse is directed. Disabled people can reclaim the word but a non-disabled man using the word in an abusive way will not be reaping the whirlwind of hatred.
"The best comment on the issue remains Herring's, whose Twitter feed is full of abuse – and praise – for making a stand. He said, 'Just a thought, but if you think mong only means idiot, why not just use the word idiot?'"
Frank Buckley, of Down Syndrome Education International, commented: "Most would consider [the word] as offensive as comparable terms of abuse referring to racial background or sexual orientation."
Penny Green, director of the Down's Heart Group charity, added: "I refute his suggestion that the word has changed its meaning. We come across people every day who still think the term applies to people with Down's.
"His actions have proved incredibly upsetting and distressing to families of disabled children, as we've seen on Twitter and our own forums. Ricky is telling everyone it's acceptable to use this derogatory term."
Tom Chivers, assistant comment editor at the Daily Telegraph, said: "Louis CK recently, a splendid American comic who discusses the use of really offensive terms, like 'f****t' and 'nigger', with wit and insight.
"But Gervais isn't using the word cleverly, to make a point, as far as I can see: he's just using it, in the knowledge people will be offended, and then mocking the people who are for being politically correct or behind the times.
"No-one is saying it should be made illegal to say it. No-one is saying Gervais should be prosecuted. But they - we - are saying that he should be a little bit ashamed of himself for being cruel, for being a playground bully on a grand scale."
BBC 6 Music DJ Lauren Laverne commented on Twitter: "What comic point or power does [the word 'mong'] have, if not that? If it really means nothing, why bother?"
Gervais has also been criticised for retweeting a message from a follower on the social networking site, who claimed that they had been hounded by supporters of Herring.
The follower had previously claimed that they were "howling" with laughter at the number of comments about a person "in a wheelchair drooling cos he was a mong" [sic].
Writing on his official blog, Gervais insisted that he wasn't doing anything wrong and that people were failing to grasp the change in the meaning of the word.
"I love how me using "mong" to mean "div" or "gimp" (and explaining that 20 times) has become...'Ricky Gervais abuses Down's Syndrome children'," he wrote.
"I also love how everyone is trying to get in on it too. We'll definitely see some comedians on daytime telly discussing how terrible I am, then mentioning their upcoming gig that's not selling. Good luck to them though.
"And that's another thing. All these people saying it's "disgusting" and "ban him from the telly"... They never liked me anyway. They couldn't have or they would understand."
> Ricky Gervais blasted by Richard Herring for calling people "mongs"