FASHION : Underwear Is In : It’s no longer just Madonna wanna-bes who are going public with their bras and camisoles.

Usually, I’m not one to reminisce about mortifying moments--unless they happened to someone else. But one of my own stands out in memory.

A few years ago, I visited a woman friend who was having a swim party at her house. When I realized I’d left my bathing suit at home, she told me to help myself to one of hers.

After I came out to the pool dressed in a two-piece suit, my friend let out an audible gasp. “I think you went in the wrong drawer,” she said hurriedly, ushering me back into the house. “You’re wearing my underwear,” she whispered, as a few people who were within earshot chuckled. I scurried back upstairs and changed into a one-piece I prayed wasn’t really a leotard.

Looking back, I couldn’t blame anyone for laughing. After all, like a lot of women my age, I grew up with the attitude that underwear was something no one was supposed to see. Bra straps that showed were a no-no, and prudent dressers always got a rear-view look of themselves in the mirror to make certain a slip wasn’t peeking out from under a hem. Since no one ever would see it, the reasoning went, underwear wasn’t important--unless, of course, you had an accident and ended up in the hospital, in which case you wouldn’t want to die of embarrassment with undergarments that weren’t CLEAN.

Things seem to have changed. That was clear the moment I stepped into a restaurant the other night to meet my pool-party friend for dinner.

Never one for plunging necklines or I’m-sexy outfits, my friend was wearing a soft floral print skirt with a pale, tailored blazer. But it was what she wasn’t wearing that really caught my attention: No blouse. Under her jacket she wore a lacy black bra. Every time she leaned over, I felt like a priest who’d stumbled into a nudist colony.

When I glanced around the restaurant, I saw two other women wearing similar outfits.

Rather than being the proprietary fashion statement of young Madonna wanna-bes, the exposed bra is moving into the mainstream. “A lot of women are going for the look, even if they’re conservative dressers,” said Shannon Stone, assistant manager of Lingerie for Less, a chain that sells discounted undergarments. One of their stores recently opened in Thousand Oaks.

Stone said the new shop conducted a survey of its customers and found that most of the women sporting underwear as clothing are professionals between the ages of 30 and 45. “This isn’t just something being worn by much younger women,” she said. “You’re finding this in conservative Thousand Oaks.”

This might come as a surprise to those who remember hiding bra straps or burning their bras in the ‘60s and ‘70s. And it is certainly a far cry from the power suiting worn by so many women climbing the corporate ladder during the ‘80s.

“I think one reason the lingerie business is so good now is that women have dressed conservatively to do battle in the corporate world, and now they are wanting more of an emphasis on femininity,” said Kevin Cassidy, president of Lingerie for Less. “The camisole look has been around for a while, but it’s even more open now.”

If it were any more open, they’d be going topless.

“Everybody’s showing their bodies more now, but some of it really has gone too far,” said 18-year-old Karen Dickerson. “I’d wear a camisole showing, but not that.”

Marianne Kniss, 38, of Oxnard, expressed similar disapproval. “I think it looks tacky,” she said. “Maybe I’m just old-fashioned, but it looks like they’re in their underwear.”

The fact is, they are in their underwear. And now that this look is becoming more common, I’m wondering what women will do next to raise eyebrows.

The only thing I can think of is to wear a bathing suit top under their blazers by mistake.

Now that would be really embarrassing.