Brassy, bombastic and cheerfully vulgar, Steven Antin’s “Burlesque” is like a Las Vegas casino show on steroids—a piece of glitzy trash that presumably aims to be campy fun but fails miserably to achieve even that low ambition.

Certainly Antin can’t expect his hokey script to be greeted with anything but derisive laughter. His heroine, Ali Rose (Christina Aguilera), is an ambitious young thing recently arrived in Los Angeles from Iowa, dreaming of hitting the Big Time. She stumbles on a joint on Sunset Boulevard called the Burlesque Lounge, where Tess (Cher) presides over a bevy of scantily-clad babes who bump and grind in elaborately choreographed routines while lip-synching to old and new favorites. Smitten by the place and anxious to work there, Ali bonds with hunky bartender Jack (Cam Gingandet), who helps her get a waitress gig. But of course Ali’s aiming higher, and before long scores a spot in the chorus line—courtesy of the unexpected pregnancy of nice Georgia (Julianne Hough). And when resident diva Nikki (Kristen Bell) tries to sabotage her solo turn, Ali belts out her song so spectacularly that Tess immediately revamps the entire show to center on her, and Our Gal quickly becomes a sensation. She also moves in—platonically—with Jack, whose fiancé is conveniently off in New York acting on Broadway.

But Ali’s rising star still won’t be enough to save the Burlesque, because as it happens Tess is heavily in debt, and her ex-husband and co-owner Vince (Peter Gallagher) is pressuring her to sell to real estate magnate—and regular customer–Marcus (Eric Dane), who has his eye not only on the real estate but on Ali. Can Ali possibly help Tess find a way to save the Lounge? And will she allow herself to be seduced by Marcus, or rather find a way to link up with Jack, the man she’s obviously destined by every convention of musical drama to be with?

You can see what’s going to happen in “Burlesque” from a mile away, because Antin frankly isn’t interested in playing with the hoary old clichés but merely in dressing them up in sequin and dominatrix-style leather tights. The plot of the movie is a throwback to the days of scenarios as ancient as “let’s put on a show!” and is obviously not worth taking at all seriously. One hopes he didn’t intend anyone to.

But surely it could have been pulled off without the strands of lame dialogue, reams of dumb narrative turns and periodic bits of idiotic melodrama that Antin’s filled the script with. And he could certainly have fleshed out the characterizations that would have been hooted out the door even in Scriptwriting 101. In addition to the stereotypes already mentioned, there’s a gay wardrobe guy who’s always making cutting remarks but dearly loves Tess (who else but Stanley Tucci?) and an emcee whose odd attire symbolizes the place’s sexily retro feel (get Alan Cumming—he’s done “Cabaret,” after all!).

Still, one can’t complain overmuch of the dreadful expository sequences, because the real raison d’être of “Burlesque” is the constant stream of musical numbers, which are staged with the sleazy sheen and ear-splitting volume of Las Vegas and shot by Antin and cinematographer Bojan Bazelli (and edited by Virginia Katz) with the maniacal pizzazz that’s more characteristic of the music-video mentality than anything else.

As for the cast, Cher does what she does—pose as a force of nature. She has one musical number near the beginning, but otherwise is pretty much relegated to sideline status as Tess watches Ali shine. Aguilera sings a lot at tremendously high volume, which will probably please her fans and should even meet with the approval of those who don’t much care for her vocalism, because at least the musical numbers give you a respite from watching her try to act. Gingandet and Bell are compelled to embarrass themselves in a couple of particularly awful scenes (like the one where he confronts his fiancé or the one in which she confronts Tess), and they don’t entirely retain their dignity in doing so. As for Tucci and Cumming, they’re playing parts they could do in their sleep—and apparently are.

But given the constant din “Burlesque” creates, sleep is something no viewer will be able to find respite in. So just be patient and wait a few minutes for the next howler Antin provides for you to crack up over. That’s the only way you can make the movie—an attempt at “Cabaret” that turns out to be more like “Showgirls”—at all tolerable.