Ricky Gervais' bad day at the office

In The Office he did an impression of an amoral middle manager staring into the abyss. Now Ricky Gervais is doing a similarly convincing impression of an offensive comedian facing career meltdown after a string of off-colour jokes has drawn heckles from disability groups, comedians and fans.

The controversy began on 29 September when Gervais rejoined Twitter, having given up after six tweets in January 2010. Four days – and a flurry of tweets involving variations on the word "mong", "div" and photographs of himself pulling "monged-up" faces – later, he was embroiled in his first row. A number of his followers had taken offence at his frequent use of the word, a shortening of "mongoloid", an offensive term for people with Down's syndrome.

Gervais responded immediately on Twitter – "Just to clarify for uptight people stuck in the past. The word Mong means Downs syndrome about as much as the word Gay means happy" – and continued in the same vein. As the criticism grew louder, he remained bullish, tweeting: "Dear fans. Don't give the haters any attention. Those people aren't really offended by the things I say – they are offended by my success."

Yesterday, the row boiled over. Mark Gale, of Mencap, said that the comedian's behaviour was "disappointing", adding that "such language can perpetuate discriminatory attitudes". Frank Buckley, of Down Syndrome Education International, told The Sun: "Most would consider it as offensive as comparable terms of abuse referring to racial background or sexual orientation."

Gervais defends his use of the word. "I have never used the word 'mongol'. I have used the word 'mong'," he said yesterday in a statement. "But I have never used that word to mean Down's syndrome and never would. I have explained, even during stand-up shows, that the meaning of words change over time. Gay, for example, would never be used to mean 'happy' any more. The modern use of the word 'mong' means 'dopey' or 'ignorant'. It's even in modern slang and urban dictionaries."

Hours later, he posted another gurning self-portrait to Twitter with the caption, "The police just came round and confiscated all my awards. Gutted."

It's not the first time the comedian has caused offence. Taboos are Gervais's bread and butter, whether it's awkward scenes involving a wheelchair user, jokes about golliwogs, getting Kate Winslet to declare that actors are "guaranteed" an Oscar if they "play a mental", or offending the assembled A-listers at the Golden Globes. As he pointed out in a blog for The Huffington Post this summer, ruffling feathers is his raison d'être.

"As a comedian I think my job isn't just to make people laugh but also make them think. I also want a strict door policy on my club. Not everyone will like what I say or find it funny. And I wouldn't have it any other way. There's enough comedians who try to please everyone as it is. Good luck to them, but that's not my game, I'm afraid."

It's a persuasive argument but as Gervais admits in his stand-up show Fame, "One false move and I'm Jim Davidson." So far, the comedian has largely got away with explosive subject matter, thanks to deft, considered and often very funny footwork. This time, though, the immediate, unthinking nature of Twitter may have resulted in a mis-step. The question is, had Davidson tweeted similar material, would he have been given the benefit of the doubt? And when does saying the unsayable become unfunny, bullying even?

In the past year, several high-profile comedians have struggled with the limits of acceptability, including Frankie Boyle. For some comedians outrage is as welcome as laughs, but when the joke is perceived to be mocking the weak, the comedian is on rocky ground, says the stand-up Richard Herring, who has been a vocal critic of Gervais's tweets. "Though there are no rules, comedy, I feel, should be siding with the weak and the oppressed and punching either inwards (at the comedian him- or herself) or upwards (at the powerful or oppressors). Punching downwards is just bullying."

It's the way you tell 'em that counts. These days, many cushion inflammatory material by delivering it in character (Al Murray's Pub Landlord), with heavy irony (Jimmy Carr) or by turning the responsibility on the audience.

Gervais's Twitter feed has opened the offensiveness debate once again. "I can understand [his] impulse to dig his heels in and say the words even more, like he's standing up to some kind of 'politically correct' backlash," Herring said. "But if the words are upsetting some people and perpetuating a stereotype, isn't it more noble and thoughtful to just admit you might have made a mistake and stop?"

It seems highly unlikely. An inveterate attention-addict, Gervais cannot have failed to notice that his followers have leapt from 68,000 to 427,000 and counting. A cynic might point out that he has a television series to promote. Next month, Life's Too Short, a seven-part comedy making light of the life of the British actor Warwick Davis, hits BBC2. "It's another naturalist observational comedy, dealing with everyday problems, human foibles and social faux pas... but with a dwarf," according to the comedian. Get ready for round two of the people vs Ricky Gervais.

Censured: From blasphemy to disability – when comedians take jokes too far

1. Jimmy Carr

The crowd was reportedly quiet after Carr said at the Manchester Apollo in 2009: "Say what you like about these servicemen amputees from Iraq and Afghanistan, but we're going to have a fucking good paralympic team in 2012." Tory MP Patrick Mercer called for an end to Carr's career, but one soldier told The Sun he "laughed out loud".

2. Frankie Boyle

Katie Price complained to the broadcasting regulator after Boyle made a joke about her disabled son, Harvey, on his Tramadol Nights show. He said: "I have a theory about the reason Jordan married a cage fighter – she needed a man strong enough to stop Harvey from fucking her." Ofcom censured Channel 4, but it broadcast no apology.

3. Bill Hicks

When the US comedian said in a routine filmed for The David Letterman Show in 1993, "If Jesus came back he might not want to see so many crosses," the whole performance was cut.

4. Stewart Lee

In his You Prefer a Milder Comedian tour he joked on Top Gear presenter Richard Hammond's accident while filming in 2006, in which he was almost killed: "I wish he had been decapitated and that his head had rolled off in front of his wife." It was called an "extraordinary attack", to which Lee replied: "It's a joke, just like on Top Gear when they do their jokes."