Peter Crawley reviews Christina Aguilera at The Point.

Christina Aguilera has apparently cleaned up her act. The pop star who reinvented herself, four years ago, as an unscrubbed sexpot in leather chaps named Xtina, has now gone (as one of her routines puts it) "from freak queen to squeaky clean".

This much-ballyhooed reform is, of course, complete tosh; her new image - a curvaceous recreation of 1940s cheesecake, all retina-searing peroxide coiffure and vampirically-red lips - is hardly any less a cartoon.

Unfortunately, a lot of fun and freedom has ebbed away with the rebranding.

Where "Dirrty" Xtina was a rude joke we could all share, "Back to Basics" Christina wears her new look like a shield. In every sense, she is less revealing.

That retreat is clear from her entrance. Hidden behind the brim of an ice-white fedora and flanked by a coterie of dancers, Aguilera descends a staircase to the tremendous horn-blasts of Ain't No Other Man.

For all the force of the brass, it's no match for her voice, an instrument of astonishing power and note-perfect control. Delivering her sustained, melismatic vocals may force her to double over, as though winded by a sudden punch to the gut, but the effect is always worth the effort.

Much like the album it serves to promote, however, the concert becomes stilted and confused by too much unguided effort.

A thematic grab-bag, it judders from sepia-hued jazz for Back in the Day and Come On Over, to Jamaican dancehall for What A Girl Wants, to somewhere between cabaret, circus and burlesque for Welcome.

There are so many ideas here, but such little coherence, that almost every routine ends, perfunctorily, with a trapdoor escape. The night begins to feel like a whole lot of nothing.

Momentum sags deepest during a po-faced video montage of obsequious fan worship ("You're one of my greatest role models!"), an ego-stroking nadir not entirely redeemed by Aguilera's sonorous turbo-ballad, Beautiful.

A pugilistic rendition of Fighter fares much better, and in the pummelling energy and unvarnished spirit of the last song, Aguilera's demure mask finally begins to slip.

This, one feels, may have proved a more certain route for going back to basics.