It's Carl Gallagher's 21st birthday and, as he strolls through the Chatsworth Estate, all cocky and confident while Muse belts out Feeling Good on the soundtrack, it seems as if nothing can cloud his horizons. He even has time to strip off his shirt to clean a car, to the delight of an audience of two - one male, one female - entranced by his obvious, ahem, charms. But when he becomes involved in shady dealings after he begs Jamie Maguire for a job (watch out for a terrifying turn from Paul Kaye as a seedy, violent club-owner), wonders if he'll live to see his 21st-birthday party. Elsewhere, it's an eye-wateringly filthy episode, even by Shameless's standards, as the half-witted, barely closeted Micky becomes enmeshed in a gay chatline, leaving nothing to his customers' - or our - imaginations.

Shameless: Brits cement their place on US screens

Transatlantic links are getting stronger all the time, as a host of new exports hits America within a week.

It would be unfair to say that Shameless (C4) has grown aimless because it was always about lives that lacked what might be called orthodox direction. When it began in 2004, with a cast that included James McAvoy, Anne-Marie Duff and Maxine Peake, one of the show's obvious charms was a manic, scattergun energy that refused to conform to any preconfigured narrative or moral shape.

Here was the underclass in all its feckless, drunken, irresponsible, irrepressible, resourceful, violent and promiscuous splendour, and there were no homilies or apologies or tales of transforming personal growth. After all the plastic melodramatics on EastEnders, this was a series that revelled in mundane minor victories over an absent landlord state: dole scams, housing benefit fraud, disability swindles.

What's more, in Frank Gallagher we heard the slurring, finger-jabbing voice of Asbo Britain. He was an antihero for our times, rat-like in his cunning and rat-arsed in his habits, a man whose waywardness made Yosser Hughes seem like Alan Partridge. Frank was a brilliant creation, not just emblematically but in terms of the story itself. His chronic dysfunction lent a tragicomic grandeur to the Chatsworth Estate.

The anticonscience is a tough act to maintain, however, and after seven years Frank's no longer just a drunken bore. He has also become boring. The show has come to rely on his ranting dereliction as a kind of dramatic prop, a lifeless symbol of continuity, like Ena Sharples's hairnet. And as Frank has become louder and more obnoxious, the other characters have also been sucked into caricature.

Last week the first five episodes of the new series played out on consecutive nights in a story that had Frank appearing in a variety of classic film and TV settings - Close Encounters of the Third Kind, Alien, Dr Who - but it turned out that he was drugged up in a psychiatric unit, where he'd been sectioned by his ex-wife Monica.

Yet even within the "reality" of the mental hospital, the film-makers couldn't resist pastiching One Flew Over the Cuckoo's Nest, with Frank recreating Jack Nicholson's role as the rebel patient Randle McMurphy. In fact all five episodes were awash with hallucinations and dream sequences, a disorienting prospect at the best of times, but deadeningly exhausting over the course of a week. It was as though jumping the shark - the moment at which a long-running TV series collapses into absurdity - had been turned into a marathon sport.

Everything about the new series - from the surreal film references to the relentlessly transgressive plotlines and the coarse, preachy tone - spoke of a frantic desperation to be meaningful. In seeking to demonstrate an urgent sense of purpose, Shameless may not have lost its aim, but it has lost its point.

So many shows aim for the twin peaks of comedy and drama and end up in a painful split between the two that it can look like an impossible balance to strike. And then back comes Shameless (C4) to show how it should be done.

It's hard to think of another show that could pull off a storyline about a family mourning the death of their soldier daughter in Afghanistan and not have you throwing your hands up in horror at rank tastelessness when the 'death' turns out to be fake. But, where the Gallaghers are concerned, all is fair in love and war, and the demise of the much-missed Debbie turned out to be just another scam. It was wrong but, in the context of Shameless, exactly right.

The downside to this twist in the plot was that it meant the return of Monica, unfit mother of the Gallagher clan and a character who is a grubby step too far, even by my sloppy standards. Monica is the device the Shameless writers use to remind us that, just when you think the moral bar can be set no lower, there is always another notch on the depravity register we can sink to.

You yearn for the day when Monica gets exactly what's coming to her. And there's the rub of Shameless: you care about the characters, even the ones you wouldn't turn the hose on (that's the clean version) if they were on fire. It's what soaps do when they're at their best, so screening Shameless every night is a smart move, giving each storyline a chance to build up a head of steam.

In a perfect world there'd be more of Mickey, Kelly and Lillian and less of Frank going doolally (again). But Shameless, with its deranged mix of gangster violence and X-rated comedy, still wipes the floor with most other attempts to show 'real' people on TV, even when it's going off half-cock.

The eighth series of Paul Abbott's council-estate drama gathers a little momentum with this second episode. Frank (David Threlfall) is still Awol after his hedonistic stag party, as it turns out with good reason: he appears to have fallen, via his stag misadventure, into a parallel dimension. Back in the real world, Libby (Pauline McLynn) is unhappy with Monica (Annabelle Apsion) for demanding custody of Liam (Johnny Bennett) and baby Stella. Continues every night this week before settling into its weekly Tuesday night slot.

The eighth series [of Shameless], which began brilliantly last night, is to run for 22 episodes (the first five on consecutive evenings), which is much more them than us, and an indication of Channel 4's enduring faith in Paul Abbott's extraordinary gallery of grotesques, headed by Frank Gallagher (the peerless David Threlfall). Last night, Frank tried to come to terms with the terrible news that his daughter Debbie had been killed while serving in Afghanistan, and then with the terrible news that his ex-wife Monica had faked the news of Debbie's death, with the help of her gay partner, posing as a military policewoman. I wonder if the Americans are ready for a family as dysfunctional as the Gallaghers, who make the Simpsons look like the Obamas.

Shameless has plenty of laughs, but quality is slipping

The Gallaghers return to Channel 4 for an eighth year of Shameless with some hilarious set-pieces, but plot-lines have started to lurch toward the ridiculous.

Paul Abbott's ribald comedy-drama about the Gallagher family has been a breeding ground for strong British acting - James McAvoy, Maxine Peake and Anne-Marie Duff have all inhabited its Chatsworth estate - and the series continues to bring the novelty. The first five episodes of this eighth series are stripped across five consecutive nights, so if you've dropped out of the habit of watching, and feel Frank's errant dynasty has become too complex to follow, here's an opportunity to catch up. And what better way to start than with the wedding of the year: Frank's. But, er, where is he, exactly?

Meet the new Gallaghers

As the American version of 'Shameless' premieres, Sarah Hughes asks if US audiences will be able to warm to the rowdy clan and alcoholic, work-shy dad.

Frank Gallagher is feeling philosophical at the start of a new series of the grubby comedy drama as he quotes "snail-chewer" René Descartes: "I think, therefore I am." But by the end of the episode, the first of five running nightly, we're asking who and, more importantly, where is Frank? It appears he might have been abducted by aliens (there's a cute Close Encounters spoof as he gazes in rapture at his brightly lit mothership, The Jockey pub). As we flash back, Frank (David Threlfall) is preparing to marry nice librarian Libby (Pauline McLynn), a bright, presentable woman who is, for reasons that simply cannot be explained, prepared to hitch her wagon to this singularly revolting specimen of manhood. But the wedding preparations are thrown into disarray when the Gallagher household receives terrible news.