The Hi-de-Hi! fan in me wanted to like Big Top (BBC1), the unashamedly 70s-style sitcom with Amanda Holden and Ruth Madoc and John Thomson, but it was just unashamedly lame. Surely if you have a circus comedy, the challenge is to create the world's first funny clown? Would putting ferrets down his trousers help? No it wouldn't. I couldn't believe Tony Robinson (Erasmus, the odd-job man) spent all those years of training on Blackadder and those archaeology programmes for this.

When I was a child, wintry Sunday evenings meant watching Last of the Summer Wine while eating my supper, snuggled up to the radiator. It wasn't so much the thrill-a-minute antics that held me in thrall as the gentle rhythms of Peter Sallis's voice, later employed to such wonderful effect by Aardman. "More cheese, Gromit?" Certainly, but if you don't mind, I'll stick to the Stinking Bishop rather than the terrible stench wafting over from Big Top.

One can only imagine that the BBC commissioners are hoping to recreate the feeling of warmth engendered by Cleggy, Compo and Foggy with this throwback of a comedy, and the cheese gauge is certainly set on full fat - but the gags are never more than inanely mild.

To judge by her hotpants and hunting jacket, Amanda Holden must be the ringmistress of a circus whose acts we never see but which sounds, from behind the scenes, where the action takes place, frankly, rubbish, despite an all-star cast. The Thompson twins, Sophie (of EastEnders, and, erm, sister of Emma fame) and John (Cold Feet and Coronation Street, though admittedly a Thomson without the "p") are married circus clowns - Helen and Geoff - who, we are constantly told by Erasmus (Tony Robinson, in an odd-job role I could never quite put my finger on), would bring more joy to the assembled crowds by leaving the ring rather than finishing their act. Ruth "Hi-De-Hi!" Madoc finally drains any goodwill her campers might still hold for her as a demanding grande dame who can't keep her dancing dogs on a leash; and Bruce Mackinnon harks back to the benign world of Alf Garnett as the idiotic acrobat Boyco, from Eastern Europe. (Thank you for the geographic tip, BBC press release.) Bruce who? Oh, come now, Bruce Mackinnon... you know, that one from The Office and The Catherine Tate Show. Still no? Me neither.

Sorry, did I say benign world? I meant disturbingly racist world. Eastern European, is he? He'll probably have a funny accent. Oh, he does. And he's casually homophobic in a nonsensical way? ("That homosexual pop group ... Coldplay.") Of course he is. But that's OK. Because he's Eastern European. Any particular country? Apparently not. But then, as stupid and offensive as Boyco's character is, it's no worse than the rest of this trite bunch. Did you not know that everyone who works in a circus is dim?

One could dwell on the curiosity of Holden's Botoxed face not allowing her a full range of gurning (or, indeed, any expression at all); on a paucity of imagination (one of Madoc's dogs is called Fido. Fido, for goodness' sake); on the offensive and pathetic punchlines (Geoff: "When we come in, you're supposed to play Looney Tunes, not ..." Erasmus: "... Hitler's speech to the 1935 Nuremberg Rally." Do we really need the date as detail - in case we thought it was a different rally? Is that speech even comedy fodder?); on the repeated attempts to get a laugh from a story straight out of a Victorian music hall about sticking ferrets down trousers ("Looks like they had a ball." Ho ho!). But to go on like that would be cruel.

After a week of such iconic women in their pomp, it is odd to come back into a world that has Big Top - the new sitcom starring the Britain's Got Talent judge Amanda Holden - as part of its cultural furniture. And at 7.30pm on BBC One, this is a big, spendy piece of furniture: like a wardrobe from Heal's, or a new double bed.

Last seen in a dramatic role as she unexpectedly burnt to death in Wild at Heart on ITV1 while trying to save a trapped giraffe, Holden's return is in a no-less baffling set-up: as "Lizzie the Circus Maestro", she runs a circus of what appear to be educationally subnormal friends and relations, in the "north Staffordshire area".

Despite a cast list of putative all-killer no-filler - Tony "Blackadder" Robinson, John "Fast Show" Thomson, Ruth "Hi-di-Hi!" Madoc and, in the first episode, even the handsome Patrick Baladi from The Office - Big Top comes from a school of sitcom acting where technique boils down to saying the words LOUDLY and rolling your eyes - much like Brian Blessed asking for a glass of white wine in the pub, on behalf of a male companion. The fact that there's a "comedy foreigner" who gets his words mixed up, and Thomson has to deliver lines such as "We need to catch those escaped ferrets - without the audience noticing!" only adds to the viewer's liverish sense of doom.

Of course, in the scheme of things, quibbling about the supporting cast here is like kicking up rough about the bread in your s*** sandwich: this is a sitcom starring Amanda Holden. I don't want to be proscriptive about comedy (it's a wide church, it's a deep well, it's often a mystery) but, by and large, it tends to be the preserve of people who can move their faces around a bit. Who knows the reasons behind it, but here Holden has as much facial motility as a seized gearbox. When she bangs home a punchline, it's like watching someone play Tetris at half-speed. I've seen tectonic plates break into a smile faster. She does, however - despite working in a big tent full of sawdust - wear incredibly tiny miniskirts and strappy heels throughout.

At the end of half an hour, a quick burst of data input into the standard-issue Viewer's Calculator reveals that, were the awfulness of Big Top rendered into miles, we could use it as a bridge to the Moon.

Do we really have to speak about Big Top? OK. Big Top is a sitcom about a failing circus, inexplicably starring the wooden, joke-killing Amanda Holden as the scatty, though apparently strong-willed, owner. There's a trapeze artist madly in love with her, Ruth Madoc as a dog-handler, and other rather good actors (Sophie Thompson, John Thomson) flailing with a lame script. Patrick Baladi as a health and safety advisor was ejected at the end of episode one after failing to persuade Holden of the merits of a life of mortgage trackers and convention. Lucky him. Poor us.

Big Top, a new sitcom set in a travelling circus, is one of those programmes that get you wondering about the commissioning process. You'll need something to entertain you while it's on and speculating about the way it came into being will do as well as anything, unless you've got a dog that's overdue for a combing or some socks to pair up. One assumes that the performers' names came first on the pitch document. One certainly hopes that they came first on the pitch document, since the idea that it was sold on the essential concept and a sample of the writing seems implausible, to say the least. We've thought of a vehicle for Amanda Holden, somebody said, and what's more it's a role that will make it feasible for her to wear hotpants and black stockings nearly all the time. And if you bite there's a good chance that we can bolt on John Thompson, Tony Robinson and Ruth Madoc. How's that for belt-and-braces coverage? Cold Feet, Blackadder and a dab of Hi-De-Hi! behind the ears.

"So what's the sit?" asks the commissioning editor. Down-at-heel circus, replies the pitcher, run by Lizzie, a mildly over-controlling ringmistress who's the only grown-up on payroll. There's a terrible husband-and-wife clown act, a depressive East European acrobat with a crush on Holden's character, a cynical soundman called Erasmus (Tony Robinson) and the self-seeking Welsh dame who does a performing-dog routine. Oh, and it's written by Daniel Peak, who wrote Not Going Out, so there's a bit of pedigree there. Lot of running gags, lot of slapstick, comedy of types. Think Dad's Army with red noses and spandex tights. And then, one guesses - since it's not very often these days that sitcoms get green-lit without jumping through this particular hoop - there would have been a rehearsed reading of the script, so that a collection of executives could mull over its prospects. And it's at this point that speculation hits an obstacle. How could they sit in the presence of gags this lame and character depiction this arbitrary and not say no?

It does go out at 7.30pm, so it's possible that the younger audience will be advanced as an alibi. It seems heartless to use children as a human shield in this way though, and surely they deserve better than gags about ferrets down trousers and punch lines that audibly creak as they're winched into place. "I was so worried that you'd fail us on the raw sewage round the hot-dog stand," blurted out Lizzie when the health and safety inspector gave her the all clear, a line that not even Helen Mirren could have made psychologically plausible. And without an underlying psychological plausibility (the urgent cartoon drives that you'll always find in Hi-De-Hi! and Dad's Army if you dig deep enough) it just isn't comic. That line isn't an inadvertent revelation - it's hopelessly, mechanically advertant, only there to be funny. In the end, an exchange between Plonky the clown and Erasmus offered the best verdict: "If we're so terrible why do we get a big cheer when we finish?" "I think you've answered your own question there."

Suddenly it's like the 1970s all over again, at least in TV sitcom land. If it's not Miranda gurning to camera and tripping over her giant feet, then it's Amanda Holden in fishnet tights and John Thomson shoving ferrets down his trousers. Which, sadly, is not a scene from a retro fetish club night but what passes for comedy on the fantastically rubbish Big Top.

The Office must have seemed another lifetime to Patrick Baladi when he found himself stranded amid the spit and sawdust as a health and safety officer in a circus sitcom so old-school it made Last Of The Summer Wine look raw and edgy. Assigned to the unenviable task of romancing Holden's dull ring mistress - think school ma'am on a hen night - Baladi was confronted by a box of dog poo. No, seriously, that was the punch line of the best joke of the night.

It was the once mighty Gladys of Hi-de-hi (aka Ruth Madoc) who was proffering the said turd, which made you feel for the talent being frittered away all round the ring. Sophie Thompson is a talented comic actress, but she has an unhappy knack of ending up in total turkeys and she's picked another one here as Thomson's clueless co-clown.

It was as though The League of Gentlemen had never happened. You can squeeze laughs out of clowns without resorting to abusing furry animals - the consistently excellent Modern Family had a great running gag about coulrophobia last week - but Big Top isn't anywhere near that league. The title isn't even a joke: it might have worked if Jordan was playing the lead but as it is it's just plain lazy. Another tent-peg in the coffin of the British sitcom (it's got so bad, I've even started laughing at Miranda. But that's probably the medication).

TV ratings: Big Top draws 3.3 million

BBC1's Amanda Holden sitcom launches against strong ITV1 opposition.

You won't have seen many adverts for Amanda Holden's Big Top, BBC1, 7.30pm, because the BBC are embarrassed about it. Correctly. It's worse than it sounds. That's worse than a sitcom featuring Amanda, Tony Robinson and Ruth Madoc in a circus sounds. Think on that.

With Britney Spears and Take That going down the circus route for their recent albums, suddenly the big top's back in vogue. But even if it didn't feature Ruth Madoc as one half of a dog act (the other half being a West Highland terrier called Dave) the ghost of Hi-de-Hi! hovers over this show.

Like holiday camps, a circus - where this is set - is like a sheltered environment where all kinds of eccentrics can live in safety, at arms' length from the outside world. The genial folk at Maestros appear to have been preserved in aspic from some time in the 60s and their biggest star seems to be Amanda Holden in a ringmaster's outfit.

Also on the bill are Tony Robinson as a grumpy caretaker named Erasmus, leotard-wearing Boyco, (Bruce MacKinnon) and John Thomson and Sophie Thompson (not related) as a pair of clowns, Jeff and Helen.

The gentle comedy tonight revolves around some ferrets down a clown's trousers and a visit from a health and safety officer - who's played by a seriously bemused-looking Patrick Baladi.

Hear that? It's the sound of arthritic gags trying to pull themselves up from the bottom of a deep barrel. Welcome to Big Top. Amanda Holden plays the ringmistress/owner of a terrible circus full of pathetic acts, so there are plenty of broad, wheezing jokes. The grumpy clown puts ferrets down his trousers! The acrobat has a comedy Russian accent! As you feel the last of your life force drain away and you decide eight-year-olds will love Big Top, it spoils everything with an off-colour routine about sleeping with a health and safety inspector in return for a good report. And if anyone thinks that will pass safely over the heads of tinies, then I beg to differ.