Opposites attract when uptight producer Abby Richter (Katherine Heigl) is teamed with loutish TV personality Mike Chadway (Gerard Butler) in The Ugly Truth. (Sony Pictures)The Ugly Truth is a flabby battle-of-the-sexes comedy that can barely work up the energy to swing a solid punch. True, its Venus vs. Mars premise is as predictable as a 30 Rock Emmy nomination, but if you're going to trot out the old formula yet again you've got to put a little more oomph into it. This movie from the makers of Legally Blonde pits cool Katherine Heigl against laddish Gerard Butler in what promises to be a juicy feminist/macho pig smackdown – think Naomi Wolf slugging it out with Howard Stern. But it turns out the Heigl and Butler characters are pushovers. Her ice queen melts faster than a sundae in a heat wave, while his half-hearted Neanderthal spouts the kind of benign insights found in Rob Becker's Defending the Caveman.

This movie pits cool Katherine Heigl against laddish Gerard Butler in what promises to be a juicy feminist/macho pig smackdown. But it turns out their characters are pushovers.

Heigl plays Abby, the super-efficient producer of a bland TV morning show in Sacramento. Butler is Mike, a slovenly shock-jock who pontificates his sexist views on a public-access cable program called The Ugly Truth. She's a Red Bull-sipping anal-retentive. He delights in scatological puns. She dresses like a librarian and has a cat called d'Artagnan. He likes to frolic with bikini-clad bimbos in a pool of cherry Jell-O. When, despite Abby's horrified protests, her boss hires Mike as a commentator to spice up her show, we're ready for the sparks to fly.

However, Mike and Abby have barely swapped insults ("Control freak!" "Manwhore!") before lovelorn Abby has caved in and turned to her enemy for dating advice. She's just spotted a slice of beefcake living next door – a dreamy orthopedic surgeon named Colin (Eric Winter) – and, given her past lack of success with men, she reluctantly agrees to try Mike's go-for-the-gonads method.

Mike remakes Abby's image into his idea of a universal male fantasy – essentially, a Britney Spears clone – then secretly coaches her, Cyrano style, when she goes on a first date with her hot doc. As the conspiracy progresses, the screenwriters (Nicole Eastman, Kirsten Smith and Karen McCullah Lutz) start piling on the raunch. Things reach a (literal) climax when Abby dons a pair of remote-controlled vibrating panties prior to a dinner engagement with Colin and her network superiors. The resulting orgasm-in-the-restaurant bit is an example of the lazy writing here – it's a blatant rehash of the famous routine in When Harry Met Sally, saved only by Heigl's game effort to best Meg Ryan's ecstatic moans.

However, that turns out to be the movie's highlight. The rest is a slog as we wait for Abby and Mike to finally realize their insults have really been mating calls. I spent the time pondering Heigl and Butler's waiting-to-jell screen careers.

Grey's Anatomy star Heigl, who made her big feature-film breakthrough in 2007 with Judd Apatow's hilarious Knocked Up, is still searching for a satisfying comic persona. After that movie (in which she played, in her own words, a humourless shrew), she went out of her way to be sweet and vulnerable as the perpetual bridesmaid in last year's sugary 27 Dresses. The Ugly Truth is another variation on that role – the uber-competent but romantically challenged heroine – and once again she's too eager to please us. In her strenuous efforts to be giddy and charming, she undercuts the uptight qualities that make Abby a suitable foil for Butler's glib slob. Heigl may just have to accept the fact that she's much funnier as a bitch.

Mike (Gerard Butler) frolics with some friends in The Ugly Truth. (Sony Pictures)Butler shows a similar lack of commitment to his part. Having bounced between rugged guy pix (300, RocknRolla) and weepy chick flicks (P.S. I Love You), the Celtic hunk now gives us a middling amalgam of both. His Mike is a coarse lout with a wounded heart under all that ginger stubble and macho bluster. (Interestingly, it takes another Scot – late-night host Craig Ferguson, in a cameo appearance – to finally finger the obvious source of Mike's misogyny. You'd think Abby would've figured it out straight off.) I remember seeing Butler in a London revival of Tennessee Williams's Suddenly, Last Summer a decade ago and I suspect he’s a more interesting actor than his limited movie roles suggest.

Director Robert Luketic and his writers (two of whom – Smith and McCullah Lutz – also penned The House Bunny) seem to be trying to steer a course between Apatow-style crudity and the witty duelling of classic male-female antagonists, from Tracy and Hepburn to Beatrice and Benedick. The result is a picture that doesn't work either way. The dialogue has as much sparkle as flat champagne, while the tepid television station scenes make you want to go home and fire up a DVD of Will Ferrell's sublimely silly Anchorman. That said, there is some spot-on character work from John Michael Higgins as the pompous Regis Philbin type who anchors Abby's show, and the always-enjoyable Cheryl Hines (of Curb Your Enthusiasm) as his high-maintenance co-host/wife.

It could be that the creators of The Ugly Truth wanted to subvert stereotypes. But if Mike the leering horndog is really a decent guy, aggressive feminist Abby is revealed to be simply an older cliché – the sex-starved spinster who, given the chance, will jump at a pair of vibrating panties. Maybe the real ugly truth is that Hollywood is just as sexist as it ever was.

The Ugly Truth opens on July 24.

Martin Morrow writes about the arts for CBCNews.ca.