Marc Blake: In hard times, it's the Gavin and Staceys we want to snuggle up to

Modern sitcoms may seem cutting age, but they are more conservative than ever. And they are driven by old-fashioned virtues

Gavin and Stacey (BBC)

The new series of Gavin and Stacey (BBC1, 9pm, Thursdays) represents a high-water mark in a return to the kind of cosy domestic comedy not seen since the 1970s, when Terry battled with June and Tom bullied Barbara in Surbiton. This will no doubt delight BBC chiefs, struggling for ratings with a dwindling terrestrial audience and an increasingly untenable licence fee. No matter that series three is over-reliant on caricature and catchphrase, or that the drama outweighs the comed: it will no doubt continue to garner plaudits and awards – and deservedly so. It is a triumph of the form.

Some say it is not real sitcom. True, the characters are not tied to a single location. They have now moved from Essex to South Wales, in what is either a bizarre act of downwardly mobility or the inevitable consequence of the credit crunch. Nor has their situation remained the same. Gavin (Mathew Horne) and Stacey (Joanna Page) at first conducted a long-distance relationship by phone, then met, then got together and then married. As a TV couple, they are insipid and ordinary and, almost unforgivably, they are happy. Not for them the will-they-won't-they-get-together, which is a staple trope of sitcom – Niles and Daphne (Frasier), Tony and Debs (Men Behaving Badly) or Tim and Dawn (The Office). This function is instead left to their corpulent echo couple, Smithy and Nessa, played ably by James Corden and Ruth Jones, also the creators of the show. Lastly, there is a narrative drive in Gavin and Stacey that takes us on a journey instead of keeping the characters trapped in stasis. There are real dramatic issues, such as what will happen to Nessa and Smithy's child (a plot device now firmly at the centre of the show), and the questions over Gavin's relocation to Barry and the sustainability of his friendship to Smithy. These issues will have to be resolved. The characters will have to compromise and make decisions and therefore mature and change – which lifts them out of this genre. However, for now, it works, and we're glued to the Shipmans and the Wests.

Gavin and Stacey has bedded into the public consciousness more quickly than most sitcoms, which tend to survive despite critics and commissioners. Fawlty Towers took four years to get re-commissioned; likewise Only Fools and Horses and Dad's Army were panned by critics. The recent ubiquity of Horne and Corden in their puerile self-penned sketch show series (Horne & Corden) and their crass horror comedy film (Lesbian Vampire Killers) were unlikely to attract more viewers, so what brought the audience in? I believe it is love – not for their cod Laurel and Hardy act, but the love written through the middle of this sitcom like a stick of rock. It's the love between Gavin and Stacey and the love of Gavin for best mate Smithy; the love within the Shipman clan and the Wests, and even Bryn, who is a lovely man. Just as with its natural predecessor, The Royle Family, these feelings are familial, non-judgemental, caring and forgiving. Of course, because we are British, they must be hidden under layers of sniping and bitching and only truly expressed in the briefest of glances or exchanges. It is here where the writing reaches the heights of Alan Ayckbourn and Alan Bennett, or the genius of Galton and Simpson.

Gavin and Stacey also takes us back to that other fundamental staple of sitcom, family. Whether real (Royle, The Simpsons) or surrogate (Dad's Army, The Office), the many permutations of the familial relationship are what intrigue and beguile us and we can never have enough of it. This is because sitcom is essentially conservative with a small c. It is not a reactionary form and, even when it does break taboos, it tends to swallow and make them palatable. An example of this is in Ideal, a sitcom starring Johnny Vegas as a minor drug dealer. Here, he is made so hopeless and in thrall to a venal girlfriend and idiot clients that we love him all the more for it. Challenging sitcoms, such as Pulling or Nighty Night, get axed or buried in the schedules.

Sitcom aficionados cite the American model for boundary-pushing comedy, with its snappy one-liners, pace and its sheer slick wit. Sure, the wonderfully dark Curb Your Enthusiasm is outrageous, but HBO does not have the same constraints as us, and besides, this is a sitcom about a man who is bored with being rich and yet who still wallows in celebrity: hard to see this working here.

What we are being invited to view in sitcom is a morality play for our times. Instead of medieval mummers parading from town to town, we have TV comedy to offer a set of ways to behave. The message is clear in US sitcom when you get the "moral moment" (around minute 19) in which the action stops, everyone hugs and considers the lessons they have learnt. We eschew this display of sentiment, but the signs are just as clear. We may prefer losers but we must accept our lot and not get above our stations.

Sitcom seems at present to be saying that in a time of uncertain employment prospects, surrounded by rapacious bankers, deceitful politicians and unreliable insurance, we crave safety and comfort. We want snuggle TV, which is why we like Strictly and X Factor, which offer glamour from the side of the stage, rather than Big Brother, whose limping penultimate series attracted no media coverage whatsoever. We're sick of looking at ourselves, pressing the red button, getting interactive. We want old-fashioned entertainment, which explains not only Brucie, but also the huge rise in live comedy and music, both tribute and original.

Comedy reflects the times we live in. We no longer need The Office to challenge our notions of PC, as we have kowtowed to the health and safety directives and the smokers (real and metaphorical) are all in their cages. Look at The Thick of It (BBC 2). Outrageous, splenetic and in your face, but isn't its rage at the culture of spin a trifle impotent? Wasn't Yes Minister actually a more superior satire that wore its stiletto up its sleeve rather than waving it in your face as it gobs at us from its hoodie? Peep Show too, while still brilliant, is trying too hard to put Mark and Jeremy into embarrassing cringe-making situations. It's the middle-aged dad at the teenager's party and they are both getting too old for this shit.

Snuggle TV is in evidence, too, in other mainstream output shows, Outnumbered and The Inbetweeners, which both do what it says on the tin. Outnumbered is a sitcom about an average white professional north London middle-class family with one more child than they can cope with. Sue (Claire Skinner) – is neither Milf nor Yummy Mummy, but an average mum who feels swamped and unable to live the glossy magazine lie. Pete, her husband – the ever reliable Hugh Dennis – is a history teacher who, rather than climb the management ladder to department head, just wants to teach. How wonderfully nostalgic. The kids are lovelorn Jamie (12), cross-examiner Karen (6) and fibber Ben (8). Ben is the monster. If he were middle-aged, he would be Brent or Fawlty, but he is a sweet curly mop-headed child with all the naivety, lack of guile and earnest inquiry that goes with it. Whereas a grown-up could conceivably bite his tongue and not say the unsayable, Ben simply asks, because he wants to know why we have to say sorry when we don't mean it, why his parents are nice to people when they don't like them.

The Inbetweeners concerns that time of life when you are desperate to be in with the right gang. Will McKenzie's dad left his mum and now he has had to move from his private school to the local comprehensive. He is geeky, gauche and pseudo-intellectual. The gang he falls in with are Simon, a romantic pining for the girl he will never have, Jay, sex pest and inveterate liar, and Neil, who would be better off as a pet. The first two series follow their adventures as they avoid their parents, who stubbornly refuse to die or leave them alone. The four do battle with one another and with the bigger kids, who always win, throughout their acne-ridden years. It is scatological, lovelorn, disgusting and sometimes obscene: in short accurately depicting teenage life. It is also as brilliant as Friends was, in that it shows that, once you leave the nest, your mates are your support group, no matter how dysfunctional and co-dependent they may be. Your mates are your new family.

Sitcom is in rude health. My Family is still pulling them in. The standard of the new Channel 4 showcase is higher than ever, with two series already having been commissioned directly from it. Miranda (BBC2, Monday nights) is resolutely old school, with Miranda Hart playing Miss Jones-meets-Rhoda, with Grenfell-like galumphing energy. All these are warm and cosy and ideal for cold December nights. Sitcom doesn't always challenge: it can be a warm bath – or a tin bath in the case of Last of the Summer Wine, which ran for millennia and is on a loop in nursing homes. These are trying times, interesting times if you believe the old Chinese curse, and we are hunkering down beneath the duvet. Snuggle TV is king. Sitcom is retro, and that's OK. It's just a bit of a nostalgic mid-Seventies jazz-rock kind of slump, a bit like 1975. I wonder what's around the corner?

Marc Blake teaches comedy writing at Solent University and KCC College, Chelsea. His book How NOT to Write a Sitcom will be published next year