Sex and the City, 15

The big-screen follow-up to the hugely successful television series will delight fans, but leave the uninitiated baffled

I'm not sure that the new Sex and the City film counts as a film at all. You've got to hand over money to see it, and it's got a longer running time than Citizen Kane, but otherwise it's no different from any episode of the series that brought Manolo Blahniks and Rampant Rabbits to an obsessive audience in the late Nineties and early Noughties. Carrie's punning voice-over is present and correct. The pacing, the tone and the look are exactly the same as they were on the small screen. And, like last year's major television spin-off, The Simpsons Movie, it lacks the grand, cinematic concept which might have demanded a broader canvas.

Over the course of 94 episodes, the HBO series covered every possible romantic complication, and when it wound up in 2004, all four of the central characters were awarded happy endings, so there's not much left for a film to do except unravel those happy endings temporarily before tying them up again once everyone's done some moping and hugging. It's as unnecessary as most sequels. It just happens to be the sequel to a television programme instead of a film.

After an opening-credits montage that serves as a refresher course in the series, the film begins with the quartet of gal pals living with their respective Messrs Right. Carrie (the alarmingly aerobicised Sarah Jessica Parker) and Mr Big (Chris Noth) are about to move into an apartment the size of the Versailles palace. Samantha (Kim Cattrall) has relocated to California where she manages the acting career of her toyboy Smith (Jason Lewis), but she pops back to New York every few minutes. Miranda (Cynthia Nixon) and Charlotte (Kristin Davis) both have a husband and a child each. It would be against the rules if either of them had had any more children since the television series' finale.

Then it's time for the Cosmopolitans to hit the fan. Carrie and Big talk about marriage, but they disagree about the scale of the ceremony. Samantha, the resident man-eater, is getting frustrated by having to restrict herself to one partner. Sometimes, she complains, she and Smith only have sex three or four times a week. But Miranda and her husband Steve (David Eigenberg) are lucky to have sex three or four times a year. Steve then has a fling with another woman: it's a motif of the film that the men behave appallingly, even though their characters probably wouldn't, and the women refuse to forgive them, even though their characters probably would. Charlotte, meanwhile, is there to make up the numbers. The producers must have decided that it would have been pushing it to have four steady relationships suddenly becoming shaky, so for most of the film her dramatic highlight is a bout of holiday diarrhoea.

There's no plot that wouldn't have been wrapped up in half an hour on television. The Biblical running time is bumped up by the introduction of Jennifer Hudson as Carrie's personal assistant, but she's written out of proceedings as hurriedly as she's written in, having contributed nothing to the film except a token black face.

The rest of Sex and the City is given over to slavering shots of haute couture. Conspicuous consumption was always a feature of the television series, but the film, which boasts at least three designer-frock montages, is so fixated on product placement that it isn't really about anything else. And, strangely, two of the things it isn't really about are 1) sex, and 2) the city. Michael Patrick King, the writer-director, doesn't comment on how New York has changed over the past few years, and the sexual content is a mere pamphlet compared to the encyclopedia of bedroom predilections and problems which the television series flicked through.

You'd have to write off SATC as a failure if King had set out to make a proper film. But it soon becomes obvious that he never intended it to be anything more than an encore: one last opportunity to spend time with some cherished characters before they walk off the stage for good. And on those terms, SATC is a button-pushing triumph. No film could be more carefully tailored for a girls' night out. There are laughs, there are tears, there are naked men. There are Eighties pop hits, there are cocktails, and there are enough over-priced shoes and handbags to make Imelda Marcos's head explode. More importantly, when the four heroines sit and banter about their love lives over lunchtime salads, they have all their old chemistry and timing: Cattrall, in particular, is such a twinkly comedienne that a better television follow-up might have been a Samantha sit-com set on the West Coast.

Think of the film as a reunion party. Fans of the series will wallow to their hearts' content. Anyone who isn't a fan already will feel like a gate-crasher.