JANE AUSTEN's language, wit and sensitivity to characters, class and matters of the heart are simply too perfect to alter. The structure's already built in. So, too, are the direction, the performances and the wonderful dialogue. As far as adapting her work for the screen, mess around at your peril.

Unfortunately, in "Mansfield Park," director Patricia Rozema messes around.

For the Canadian filmmaker (who made the wonderfully delicate "I've Heard the Mermaids Singing"), Austen is grist for a feminist, quasi-lesbian agenda. This would be perfectly fine as an undercurrent, but Rozema pushes the subtle Austen off the cliff of discretion. And discretion is the very essence of Austen's writing.

There's an unquestionably erotic moment between two women in the film -- almost irrelevant to the main action -- and Rozema presents a rather brazen heterosexual moment which -- for my money -- tears unnecessarily through the story's gentle fabric.

Rozema also makes her directorial presence known in other ways. She occasionally renders scenes into momentary slow motion for reasons that escape me.

Nor can I offer an explanation for why she makes the heroine (played by Frances O'Connor) address the camera directly. Because it's cute? Why this self-conscious MTV moment of intimacy? "This is 1806," as one character later reminds us. Not the 1990s.

Rozema is also working with a cast that -- to dabble in a little Austenspeak -- is satisfyingly well above competent, but unequivocally shy of spectacular.

The cast, which includes Jonny Lee Miller, Embeth Davidtz and the playwright Harold Pinter, is definitely second-tier. No one really owns, or lives in, their part, although O'Connor comes the closest.

When her impoverished family sends her to live with wealthy relatives in Northamptonshire, Fanny Price (O'Connor) finds herself a second-class citizen with the Bertrams.

But she has two avenues of immense relief: her writing, at which she excels, and Edmund (Miller), a Bertram son of similar age with whom she builds a close, undying love.

As these faux siblings grow older and closer, their relationship seems too pure to negotiate the white-water rapids of romantic love. But when other suitors appear, it's time to reconsider that purity.

When Bertram patriarch Sir Thomas Bertram (Pinter) returns from his questionable activities in the slave trade, he brings a new, negative dynamic into Fanny's life. He can't help noticing how attractive she's become, and he's not exactly receptive to her intellectual brilliance -- including her insightful observations on the evils of slavery.

She has other problems, namely the dandyish Henry Crawford (Alessandro Nivola), accompanied by his sister Mary (Davidtz), who insinuates himself into the Bertram household and proposes to Fanny almost immediately. Rejecting his offer, and incurring Sir Thomas's wrath with her refusal, she finds herself banished to her poor, estranged family in Portsmouth.

Although Rozema's screenplay respects the customary Austenisms -- that gorgeous, delicate balance of romance and irony -- it lacks the majesty of such previous Austen adaptations as "Persuasion" and "Sense and Sensibility."

The possibility of a union between Fanny and Edmund (a dedicated but somewhat wan Miller) doesn't truly engage us as it should. Yes, it would be awfully nice for that to happen, but not heartbreakingly essential. Rozema seems far more interested in a steamy moment between Fanny and Mary -- judging by Fanny's damp, sweaty flesh, her loosely tied corset strings, and Mary's long, searching gaze.

Even the humor, which ought to be the heart and ribs of the drama, seems tacked on for good measure.

"Just remember, Fanny, I married for love," says Fanny's mother, rather grimly. This is a wonderful line, especially coming -- as it does -- in the depth of Fanny's romantic despair. But this moment only reminds us that in this "Mansfield Park," the Austen zingers are few and far between.

MANSFIELD PARK (PG-13, 112 minutes) -- Contains sex and nudity. At the Cineplex Odeon Outer Circle.