Ricky Gervais was enjoying a relatively quiet time, promoting his new show, when I met him a few weeks ago at his office in Hampstead. We had a nice chat, he talked about comedy, explained in the abstract that causing offence isn't in and of itself a bad thing, then a few days later managed to offend everyone so violently that he wound up being lectured on morality by the front page of the Sun.

He had tossed out a reference to "mong" on Twitter and, when challenged, defended and aggressively reused it on the basis that the word had evolved from its original meaning and was no longer a term of abuse for disabled people. After he was corrected by Down's syndrome groups and a mother of two disabled children, he backed down. But the scale of the outrage, and his defiance in the face of it, was stoked by a lurking sense that he was in any case overdue for a kicking. "Someone even suggested it was a PR stunt," he said. "Amazing."

His office is a modest suite of rooms one floor above shop level, bare but for a desk, a chair and a rash of Post-it notes on the wall outlining episodes for his forthcoming show, Life's Too Short. When I walk in, Gervais is staring at his computer in a way that comes across as a little nervous. He lives around the corner and can be out of bed and at work in no time, which is why, though a workaholic, he gets up at 9.30am and schedules his first meetings for 11. "I'm a toddler. I need 10 hours' sleep. I'm the opposite of Margaret Thatcher." He issues his trademark laugh, that incredulous, high-pitched cackle, exposing sharp incisors in a newly lean face. "Yeah – I'm a workaholic between the hours of 11 and 3." Except when he's filming, when he starts at the impossibly early hour of 8am. "Why? What are we, farmers?" And he cracks up again.

At 50, there is something about him reminiscent of the student union entertainments officer he once was – that combination of sarcastic and giggly: half nerdy, half threatening. Reception of the new show will almost certainly be coloured by the recent dispute, though he was anticipating criticism anyway. For all his scrupulous irony, Gervais has advanced to a state of defensiveness wherein he can unjokingly say things like, "I embrace the haters." (Why? "Because it means I'm doing something right. The importance of art is to make a connection.")

The new show is similar in format to Extras and The Office, and follows Warwick Davis, "the UK's go-to dwarf", in a fake documentary about his theatrical dwarf-hiring agency. There is a lot of falling down, a lot of height gags – he can't reach the doorbell – which play both on the delusions of the hero and the inadequacy of the people around him and which, Gervais predicts, will no doubt be Taken Wrongly. "People are straight away thinking it's going to be a cruel comedy – why? Why do they assume that? It's their prejudice. People confuse the subject of a joke with the target of a joke."

He takes refuge in the controversy-as-proof-of-insight defence. It's a comedian's job, he has said, to make people think as well as laugh. Of Life's Too Short, he says, "I must admit I was excited by the fact that we owned the -ism." By which he means dwarfism. He looks thoroughly martyred. "Another taboo subject."

Gervais was 40 when the first season of The Office was made, late enough that he has retained the mannerisms of a regular guy. He was happy in his previous existence, enjoyed his job scriptwriting at the radio station Xfm with Stephen Merchant, had nice friends, lived with his long-term partner, the producer turned novelist Jane Fallon, and was more or less content to carry on like that, getting his kicks from being the funniest guy in the pub after work. When The Office got picked up by the BBC, Gervais's lack of desperation – and the fact that it represented a relatively small investment by the corporation – emboldened him to make most of the creative decisions himself. Although he looks back on his 30s and shudders at his complacency, it was never a question of fame at any cost.

He has a lot of celebrities at his disposal these days. Extras called in favours from all those A-listers who went around saying how much they loved The Office, and the same goes for Life's Too Short. In the first two episodes, Johnny Depp pops up to take the piss out of himself, as does Liam Neeson, asking Gervais for advice on how to become a standup comic. The episode with Depp draws on Gervais's infamous roasting of the actor at the Golden Globes and plays like a Hollywood end-of-term review. Did Depp have to be talked into it? No, Gervais says. "I sent him an email and said, 'Sorry about the Golden Globes, how would you like to get your own back?' He replied, 'I care not a jot, sir. I've been a fan of yours for ages. I found it hilarious. I read worse things about myself every day and it would be an honour.'"

Gervais says: "His emails are like poetry. He's made of bohemia, d'you know what I mean?" He grins. "He's such a sweet soul."

It's funnier, though, isn't it, to have a scene with D-listers like Cannon and Ball (or Hale and Pace) trying to get into the Ivy than A-listers sending themselves up. It seems like yet another layer of celebrity vanity; as well as everything else, they want kudos for self-awareness.

"Yes. Of course. That's true. On a meta-level, we know they are never really harmed by this. There's an irony shield. The more they make a fool of themselves, the less they can be like that. At the end of the day, we know they're winning."

But? "But. Sometimes, realism aside, comedically, there's something tantalising about finding the best/worst person for that gag. So when you have a sketch about the worst person ever to tell you they want to do comedy, who is it? It's our John Wayne. It's the man from Schindler's List and Rob Roy. I can't pass up that chance because people might prefer Cannon and Ball. I'm still making entertainment. It can't be democracy."

I know a lot of people who preferred Extras to The Office; it was gentler, less painful to watch. The relationship between the Ricky character and Ashley Jensen was genuinely moving and captured their best friendship in such a way that you came away from the series with a sense of both Gervais's great writing talent and his probable sturdiness as a mate. "Which would you rather have," he says to Jensen on the phone one day, in lieu of hello, "a bionic arm or a bionic leg?" and it said everything you needed to know about their relationship.

Which would he rather have? "Leg, obviously. What can you do with the arm?" He thinks about it for a second and recalibrates: "Problem is, if you launched yourself with a bionic leg, you'd throw your back out. So you'd need a bionic spine, too." He grins. He doesn't buy anything very glitzy with his wealth, but if they ever invent a jetpack, he says, he'd sell his house to get his hands on one.

Gervais is a terrific snob about the right and wrong kind of fame, and about what one does with it. For example, the celebrity cameos on Extras don't just play themselves. They play carefully crafted versions of themselves as conceived by Gervais. "Anyone can get these people in for Comic Relief. But [Extras] is part of their job, this is part of their oeuvre. It's on their IMDb page."

And he gets annoyed when he's lumped in with desperate wannabes. "I do the same red carpet sometimes as Kim Kardashian. But I'm going, 'Watch the thing I made' not, 'Look at my fanny.'" He says, "I never signed a deal with the devil: make me famous and you can go through my bins. Some people do. Sometimes they deserve it."

Not that Gervais hasn't, occasionally, done things just for the cheque. When he was still relatively unknown, he did a couple of voiceovers, for Fairy Liquid and Miniature Heroes – "Most money I'd ever seen" – and when he first got famous, he did a couple of standup gigs for corporate clients. "I didn't want to. I went, ah, it'll be horrible, and then a really weird thing: it was the same amount as my dad's salary. For 40 minutes. And then I felt guilty – who am I to turn this down? And I did it. And then I went, no, fuck that. I don't want to do it." These days he turns down advertising offers. "I'm not on my high horse, I'm not all Bill Hicks about it." But, he says, "I don't want to be famous for being the bloke in the John Smith's advert." Unless it's a favour for a friend, Gervais resents doing anything he hasn't had a hand in creating.

"I don't count it as my oeuvre," he says. "If people said, what's your job, I'd probably say The Office, Extras, The Invention Of Lying, Cemetery Junction, Flanimals, the podcasts, Idiot Abroad and Life's Too Short. Popping up on The Simpsons is great, or popping up on the Golden Globes. But I do the Golden Globes like some people play golf. Win, lose or draw, it doesn't affect me. I'm not beholden to anyone, I don't have to be nice to directors. I don't have to be nice to anyone."

His not-being-nice-to-anyone routine is the thing, in his comedy, that Gervais spends the most time justifying and explaining. If he satirises bigotry by using bigoted language, he can't be held responsible, he says, for idiots who mistake it for the real thing. Given "half the population believes God made the universe 5,000 years ago", what can you do? "Just because someone is offended doesn't mean they're right. Some people are offended by equality. Or mixed marriage. So you're offended? So what? I've got no issues. I'm not trying to offend or annoy or insult. I'm trying to have a laugh."

Still, whether or not through audience stupidity, it remains the case that some of his jokes get a large kickback off the chauvinism they purport to be satirising. The Golden Globes furore mainly focused on his jibe about Scientology, not something even the bravest comedian is usually minded to do – "I did carefully word that. I was really, really careful." In the event, the Scientologists left him alone. It was Kim Cattrall who complained about remarks about Sex And The City 2 along the lines of, "I was sure the Golden Globe For Special Effects would go to the team that airbrushed that poster. We know how old you are, girls. I saw one of you in an episode of Bonanza."

Cattrall accused him of being ageist, although it came off as plain sexism. "No," Gervais says, "it's the opposite. I don't think you lose your sensuality at 50. But why are we pandering to Hollywood that you have to look 25? The target is the opposite of what she thought." But if the effect, on a particular crowd, is to reinforce the original prejudice, the intention of the teller starts to sound a little hollow.

There is a level of success, perhaps, that makes a comedian deaf to the impact of some of his jokes and Gervais, after being called a "moron" by Deborah Orr in this newspaper and attacked by other columnists elsewhere, conceded his casual use of a term still used to ridicule disabled people was wrong. He is at pains to point out that it wasn't the hacks – "the gossip mongers, shit-stirrers and attention seekers who are jumping on the bandwagon" – who changed his opinion, but Nicky Clark, the mother of disabled children who appeared on the BBC to counter Gervais.

Given his reach, his initial defence of the word, which he worked into some ill-advised jokes to wind up his detractors – "Good monging" etc – looked like bullying and was worse than the original insult. "I was only defending it in the sense that I was sure the word had changed. And it has for a whole generation. However, if there is even a tiny chance of it still being used as a word of hate, then that's enough reason for me as a public figure to stop using it," he says now.

He hasn't spoken to Francesca Martinez, the disabled actor who worked with him on Extras and who called him out during the debacle. "I haven't spoken to anyone except Nicky Clark to put the record straight. Don't know if it has or not. If it has, fine. If it hasn't, it's just one more in the huge list of myths and legends."

It's a qualified climb-down, but then belligerence has always been part of Gervais's appeal, his faith in his own opinion a relief from so much focus-grouped spinelessness. It was his mentor Christopher Guest who, when Gervais's two films, Cemetery Junction and The Invention Of Lying, went before focus groups, reassured him he was right to ignore them. There was nothing he could do, however, when, to meet airline standards, Gervais was required ruthlessly to edit the latter for the inflight version. Every sniff of a swearword had to come out, even "gosh". He became so infuriated, he corrupted the whole process. There is a scene in the film, which is set in a world where no one can lie, in which Jennifer Garner opens the door and says to Gervais, her prospective date, "Oh, you're early, I was just masturbating." To which he replies, "That makes me think of your vagina."

"We couldn't have that," says Gervais, "so we went with, 'Hi, you're early. I was just masticating.' And I go, 'That makes me think of your angina.'" He starts rocking with laughter. "Cos I was so angry. This is fucking ridiculous, so we just started taking the piss. Someone watching on the plane will be going, what the fuck is this about?" He's almost crying with laughter. "Oh dear."

The criterion he has for starting any project is: how much fun will this be? It has to come out of play and an adrenaline rush. Parts of his career make him look like a business genius – the podcasts, say, which he, Stephen Merchant and Karl Pilkington gave away for free until, having established a multimillion-strong audience, they started to charge for them. But, he says, they weren't that clever. He did the podcast because it was funny, he missed doing radio and he could fit the recording sessions into his schedule wherever he liked. He was also curious about the new technology. "I thought, I wonder if this can work? What can I do with this? It's a new playground." At the time, when the most popular podcasts were getting around 10,000 downloads, Gervais and co attracted more than a quarter of a million listeners in the first month. To this point, he has given away 320m free downloads and sold around 5m.

That's astonishing, I say, and with a certain Orson Welles gleam Gervais replies, "Yeah, but there are six billion people in the world. Six billion. OK. When you think of a hit show on TV that might get five million – that's nothing." He won't ever admit to ratings-chasing. (This whole business on Twitter comes in the context of Gervais having left the social network a while back because it was "undignified" and rejoining only recently, he says, because "it's fun. I want to see what happens." What happens, mainly, is promotion of his products.) He insists he is not interested in hustling to get the kind of audience figures that, say, Two And A Half Men gets in the US, or My Family used to get in the UK – 10 million a week, way more than The Office or Extras. But, says Gervais, "Why would you want to be in a huge club with no door policy? D'you know what I mean? You want to be in an exclusive club. Most things are shit. Most art, most music, most carpentry is shit. But when you see a beautiful piece of furniture or a wonderful painting, you go, aaah. Oh, I get it. It has nothing in common with that other stuff. You want to be in that gang."

To ask whether success has made him insufferable is a nonsensical question, he says; it would never get to that stage, although tweets such as, "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" aren't overly endearing, even if accurate. The point is, he says, he still has his old friends, his family, his partner, Jane, all good people. "When I first came into it, I was very conscious of reputation. I thought it was everything. And now I think, no, it's not actually. Because reputation is what strangers think you're like. Character is what you're really like. And all my best friends and my family know what my character is."

It's true that the first butt of his jokes is and always has been Gervais himself. He can deliver all the highfalutin theories of comedy he likes, he says, but for most people The Office was about "a little fat bloke doing that dance". Speaking of which, is the weight loss a vain reaction to his fame? No, he says. He was thin in his 20s, when he was running around on the dole. Then, in his 30s, he bulked up – "The eating years." And then, "Christmas before last I thought enough is enough. I woke up after a sausage binge, and I thought I'm going to fucking die here, it's crazy. Nothing to do with vanity. Nothing. I play putzes in the next two films. I don't want to die. But I also don't want to give up anything. So I still eat and drink like a pig, but then work out like Rocky the next day. I'm only living longer to eat more cheese."

He has a lot on his plate at the moment: a movie version of Flanimals, his children's book – "My baby." More films in the pipeline, and the new TV show. He and Jane divide their time between the house in Hampstead and two homes in New York, but apart from that, he says, his life isn't that glamorous. Most evenings "I'm in my pyjamas with a bottle of wine open and the cat on my lap, watching telly. It's as normal as I've ever been."

• Life's Too Short starts on BBC2 on Thursday 10 November.