Bat for Lashes, Roundhouse, London, <br/>Doll and the Kicks, Brixton Academy, London

Bang that tambourine, but forget the gong: Natasha Khan can certainly shake it, but her inclusion in the Mercury shortlist embodies all that is wrong with the award

Don't blame Natasha Khan. When the Brightonian singer takes the stage at the iTunes festival, she's still unaware that in two days' time, Bat for Lashes' curate's egg of an album, Two Suns, will be nominated for the Mercury Music Prize. For now, she is just innocently doing what she does.

And what she does, without question, is give good gig. Twirling and tambourine-bashing her way across the Roundhouse stage in front of flickering, strobing banks of LEDs, wearing the sort of outlandishly fringed jumpsuit no one this side of Björk or Lovefoxxx would even attempt to carry off, she looks like some sort of Native American witch queen.

She's backed by something of a mini-supergroup, comprising artists-in-their-own-right Charlotte Hatherley and Ben Christophers plus New Young Pony Club's Sarah Jones (not to mention a section of catgut-plucking pizzicato strings), but Khan is unquestionably the leader, and a very hands- on one, budging her keyboardist along for a four-handed duet on "Horse and I", and sitting solo with a zither for "Prescilla".

The mystical imagery of Two Moons is reflected by the fairies and inflatable silver stars that bedeck the stage, not to mention wolf costumes on stage and bat masks in the audience. But the album's often subdued, Clannad-like folk-pop atmospherics are too easily drowned out by the chatter of a crowd which, having been given its tickets for free, is inevitably indifferent compared with paying partisans.

She's an engaging and impressive performer, but the album she's promoting is, in all honesty, a 7/10. Which is why it's somewhat baffling to see her given a second shot at a Mercury (her debut, Fur and Gold, having made the list in 2007). Presumably the panel sees this as its last chance to present Khan as something vaguely "new" before she turns 30 in October.

Of course, the annual announcement of the Mercury shortlist is always the cue for much enjoyably cathartic tutting, astonishment at the rubbish that did make the list, indignation at the overlooked gems that didn't, and head-scratching at the names you've never heard of. But I've never known a year like this one. Everyone I've spoken to agrees it's an absolute joke, the worst selection since the gong was launched in 1992, packed with landfill indie mediocrities (Kasabian, honestly?!) and Nathan Barley-friendly no-marks.

The whole concept of the Mercurys is fatally flawed. The arrogant conceit at its heart is that an art form as subjective as music can be mastered, tamed, weighed and quantified, and that a committee of a dozen "experts" can be locked in a room and, like Shakespeare-typing chimps, somehow arrive at a definitive list of the dozen finest albums.

The list, announced from upon high with the white-smoke pomposity of the Vatican revealing a new Pope, snootily and snobbishly sets itself up as inherently superior in quality to that chosen by the great unwashed in, say, the Brits. But there are only two valid ways of bestowing acclaim: either go completely arbitrary, or completely democratic. 100 per cent personal, or 100 per cent public. All else is delusion and vanity.

I realise that the Mercury panel is partly made up of people like myself (broadsheet critics), and that I am, to paraphrase LBJ on Hoover, outside the tent, micturating in. Long may that continue. I write in the belief that criticism can only ever be subjective, and that anyone who affects a stance of objectivity is a fool, a liar or both.

The Mercury has always been a commerce-driven enterprise, aimed at luring the fabled 50 Quid Man to step outside his comfort zone. Hence the blatant box-ticking exercise which guarantees there'll always be one jazz record, one folk record and so forth, even though the winner is invariably something from the indie end of the spectrum, with the occasional urban interruption.

Given this fact, given this year's significant female slant, and given the likelihood that the Mercurys won't wish to be perceived as following the Brits by giving Florence Welch her second award in six months, Bat for Lashes is looking a decent dark horse at 6/1 to win.

If Natasha Khan does walk away with this compromised, discredited bauble, it will be hard to begrudge her. But it will prompt the question: is that really the best we can do?

Doll and the Kicks, another female-fronted Brighton band, are a few rungs below BFL on the pecking order, being as yet unsigned, but they're getting a leg-up from a very prestigious personage.

The approval of Morrissey has historically been a mixed blessing: it paid off nicely for James, not so well for Elcka or Bradford. This year, the quinquagenarian quifflord has hand-picked the Kicks as support act on his entire Years of Refusal tour, and on the final night of the run, they've grown into contenders ready to stand alone.

The Kicks – one guy with an MC5 afro on bass, two indie blokes on guitar and drums – are dwarfed in every sense by the spidery figure of "Doll" herself. Hannah Scanlon (pictured) has the crop and staring eyes of Mia Farrow in Rosemary's Baby, and utilises her androgynous physique to theatrical effect, strutting and declaiming in her unusual voice through a set that takes in the ESG/Slits funk-noir of "You Do It Better", the Patti Smith Group velocity-rock of "Fire", the punky reggae skank of "Roll Up the Red Carpet", the Siouxsie-style yodel of "Pictures", the Duranny hi-hat disco of "He's a Believer" and the Sixties-ish tragic-ballad "If You Care".

Only once does Scanlon appear to be uneasy. A wireless monitor malfunction means a bandmate needs to hoist up her dress to fix it, exposing her knickers to the entire academy. "This isn't happening in front of thousands of people," she assures herself out loud. Get used to it.