Touched For The Very First Time, Trafalgar Studios, London

This must be the only play I have ever seen where the paparazzi have stormed the stage before the curtain call has even begun. And where the star has happily posed for them backstage for a little while before re-emerging to pose for them a little bit more, this time with the photogenic producer. Well, who needs applause when you've got the pop of a hundred adoring flash bulbs? And what else can you expect when you put Sadie Frost (ex-wife of Jude Law and drinking partner of Kate Moss) on the West End stage in a one-woman play about Madonna, produced by Imogen Lloyd Webber (daughter of you-know-who)?

In Touched for the Very First Time, Frost plays Lesley, a Northern lass who, in the absence of an attentive mother figure (too busy being a socialist feminist), turns to Madonna for female guidance as she grows up in 1980s Manchester. As the chameleonic queen of pop negotiates her route from New York club chick to disco divorcee via erotic siren and earth mother, so too does Lesley wend her way down the tricky passage to womanhood, taking Madge as her lead on everything from sex and boys to fashion, career choices and motherhood.

This device means the play opens to the rather alarming sight of the 43-year-old Frost prowling around a messy bedroom and writhing on its bed in leopard-print leggings, pretending to be a 14-year-old virgin. Once the shock has worn off, Zoe Lewis's play feels a little like watching a chronological medley of those "I heart 1984" programmes television was so keen on a while ago: a quirky encounter with ecstasy at an illegal rave here, a reference to meeting Meg Mathews in the Met Bar there. While there are occasional flashes of warm Northern wit and, in the early teenage scenes, an Adrian Mole-esque gift for laconic observation ("My mother was a feminist. She doesn't clean, because she believes in equality"), too often Lewis relies on comfy clichés to herald the passing of the years. Lesley's voice, initially endearing in its naivety – "It is my 16th birthday and I am wearing my power suit from Next and Poison by Dior" – starts to grate as Lesley ages, though never, apparently, grows up into a two-dimensional adult. Ultimately, Lewis doesn't take her material anywhere deeper than a cosy nostalgia-fest and some vague thoughts on sisterhood and girl power.

As Lesley, Frost is a surprisingly game performer. In a good-natured performance, she prances around the stage, not afraid to play the fool, dressing up in ever more ludicrous ensembles, tackling regional accents and not in the least bit squeamish about acting out some of the more sexually embarrassing tales.

She does, though, tend to rattle through her lines rather than fully inhabit them, which means that she too often misses the point of them altogether and fluffs the jokes. She suffers from a woeful lack of direction, too, forced to undertake tricky costume changes only half-hidden from view and passing the scene breaks with some awkward posing and voguing as fairy lights flash and Madonna songs boom out of the speakers.

At the end of the play, the word going around my head is "brave". But you don't come to the West End for bravery. If it weren't for the unholy female trinity of Frost, Lloyd Webber and Madonna, this amateurish production would never have made it off the fringe. Which is girl power of sorts, I suppose.

To 14 March (0870 060 6632)