"There are a lot of cute guys in this audience," gasped Britney Spears midway through the first British show of her Onyx Hotel tour. "I might marry one of you!"

Four years ago, when Spears was America's most famous virgin, this would have seemed like a witty aside. Today, it doesn't seem beyond the realms of possibility.

In the last 12 months, Spears has indulged in a spot of televised faux-lesbianism with Madonna, a swiftly annulled Vegas marriage and released a video for her current single, Everytime, which features the singer drowning in a bathtub.

One school of thought suggests all of the above were publicity stunts. The idea was presumably to convince the world that Spears was not just a fading teen star. The idea has succeeded, although not perhaps in the manner intended: most observers are now convinced Spears is not just a fading teen star, but a certifiable lunatic to boot.

That's not an impression much dispelled by the tour programme, which features Spears attempting to explain the show's "concept" in a manner that would have left James Joyce scratching his head: "Thoughts of happiness that lies within everyone tranquillises your being of being who you be of this forbidden picture of what you are supposed to show," she illuminatingly writes.

As she takes the stage, she promises the show will be "beyond your wildest, wildest imagination". In fact, what it most resembles is a West End musical with costumes by Ann Summers. There are bare-chested bellhops in braces and jackboots, which recalls The Night Porter. There is a French maid with her bum out, which recalls The Benny Hill Show. Indeed, the concert has more in common with the latter than it thinks. It knocks itself out trying to be sexy, with the net result that it isn't sexy at all.

Music comes merely as an afterthought. Toxic is dashed off as the set opener. Hit Me Baby One More Time is delivered as a tuneless burst of cod-jazz. You leave no clearer as to whether your being of being who you be has been tranquillised or not, but with the distinct impression Britney Spears has no idea where her true strengths lie.

· At Wembley Arena (0870 739 0739) tonight, then touring