Even the biggest names in fashion routinely sneak a peek at the competition, but no one has pirated designs with more panache—or more unblushing persistence—than Jack Mulqueen, 38. "He didn't get the name 'Fast Jack' for nothing," observes Saks' corporate fashion director Ellen Saltzman, who buys more of Mulqueen's elegant but comparatively inexpensive knockoffs than any other retailer. "He seems to copy collections before they are created."

Is Mulqueen embarrassed by his reputation for larceny? Far from it. "I copy only shining stars like Kenzo, Ungaro, Yves Saint Laurent, Claude Montana and Giorgio Armani," he boasts. And his copying is completely legal. Sometimes, though, Fast Jack slows down long enough to lure certain designers into a licensing agreement under the Mulqueen label. "But if they aren't interested," says Mulqueen with a shrug, "we copy them anyway and save paying them the up-to-five-percent royalty. They would be smart to cooperate." Among those who do are Mary McFadden, Zandra Rhodes and Valentino, all of whom now design dresses and blouses under Mulqueen's label—most priced below $200. "My customers are used to paying $2,500 per gown," says McFadden. "They are thrilled that I design a lower-priced line of silk crepe de chine dresses. You could say I knock myself off."

Yet such aboveboard licensing arrangements account for only 40 percent of the $225 million Mulqueen expects to gross this year. The bulk of his business comes from knocking off the cream of couture without bothering to ask permission. Each morning at his three-story headquarters in the heart of New York's garment district, Fast Jack and his team of 17 little known designers scour the pages of Women's Wear Daily for photographs of the latest $2,000 to $10,000 creations from the fashion runways of Manhattan, Milan and Paris.

In one day, 20 styles can be copied. Patterns are drawn, cut, graded and duplicated, and then sent to South Korea, where 22,000 factory workers spin the designs into sensuous silk dresses, blouses and suits. Within 10 days, 50,000 garments can be shipped anywhere in the world. "We sit here with our magnifying glasses, copy like mad and screw up the whole system," gloats Mulqueen. "Nothing gives me more pleasure than seeing 5,000 American department stores get European designs before the Europeans do." Says James Brady, former publisher of Women's Wear Daily: "He's no Saint Laurent, but Jack does more with less than anyone else. He markets the ideas of others brilliantly."

Although he numbers Faye Dunaway, Meryl Streep, Olivia Newton-John and Barbara Sinatra ("She buys right off the rack in my showroom") among his customers, Mulqueen sells primarily to young working women who cannot afford $4,000 for a Valentino original but will plunk down $150 for a nearly identical Mulqueen. Often, Mulqueen's copies are interspersed on retailers' racks with the real thing. "His dresses would be a lot less interesting," says Bloomingdale's president Marvin Traub, "if we didn't also carry the designer originals."

Not surprisingly, Armani and Saint Laurent are less than enthusiastic about helping to make Mulqueen's knockoffs "interesting." "Copies are a form of flattery," grumbles Armani, "but his quality is never as good. He's a high-class thief—he knows just what to steal." Saint Laurent's confidant and business partner, Pierre Bergé, concurs. "If America had laws to protect artists like Yves," he snaps, "Mulqueen would be in jail."

A native New Yorker, John Anthony Patrick Mulqueen, whose father owned a trucking company, began wheeling and dealing when he left Fordham University 20 years ago to sell BVD hosiery on the road. Later he helped create such off-the-rack lines as Jones New York, Jaeger and Dana Côte d'Azur. By 1977 he saw that the price of silk was rising 25 percent a year and became part owner of Kosilk of Korea, the free world's largest producer of the material.

With sales doubling every year since, Mulqueen's partnership with Kosilk is thriving, unlike his marriage: He and wife Patricia are splitting after 15 years. Until their divorce becomes final, however, the Mulqueens continue to live at opposite ends of a sprawling Sutton Place co-op. Aside from his 14-year-old equestrienne daughter, Whitney, whom he has presented with four jumping horses, Mulqueen's only remaining attachments are to hard work and high-priced amusements. He drives a $115,000 Ferrari Boxer and a $110,000 silver Rolls-Royce, and is negotiating to buy a Canadair Challenger aircraft for $7.5 million. He gambles in Monte Carlo, shops on Savile Row and dines at Maxim's. "I'm more extreme than most," Fast Jack concedes, "but like I tell Whitney about her horses: If you come in second, you might as well come in last."