NEW YORK, United States — A petition to get Gap Inc.'s Old Navy to stop charging more for women's plus-sized jeans has gathered more than 35,000 signatures online.

The petition charges Old Navy with sexism, noting that a pair of women’s plus-sized jeans can cost about $15 more than regular jeans, while a pair of men’s jeans costs the same no matter the size. Customers are also calling for Old Navy to put the larger apparel into stores, instead of just selling it online.

Old Navy said the price difference is a question of craftsmanship. The items are specifically designed and manufactured for plus-sized women and cost more to make, Debbie Felix, an Old Navy spokeswoman, said in an e-mail. The company has a separate team of designers and merchants working on its plus-sized products to adjust them for fit and style, she said. Men’s jeans don’t typically get that kind of treatment.

“Old Navy is proud to provide stylish clothing at a great price to all of our customers, including our plus-size customers,” Felix said. “These clothes are specifically designed and manufactured to fit and flatter our valued customers. While we don’t make more money on our plus-size line, our plus-size clothes cost more because we invest more in them.”

The company has an interest in appealing to plus-size apparel customers, who represent one of the fastest-growing parts of the U.S. retail industry. The market grew 5 percent in the 12 months ended April to $17.5 billion, according to NPD Group. An average American woman over 20 years old has a 37.5- inch (95-centimeter) waist, according to the U.S. Centers for Disease Control and Prevention. Plus-size clothing generally constitutes sizes of about 18 and up in the U.S., and Old Navy’s plus-size chart starts at a 37.25-inch waist.

Other retailers are increasingly trying to appeal to larger customers. Calvin Klein used plus-sized model in its recent underwear campaign, and Hennes & Mauritz AB did the same with its swim-wear line last summer. Even Abercrombie & Fitch Co., known for targeting slim-waisted college students, has reversed its earlier stance and begun offering larger sizes online.

By Lindsey Rupp; editor: Nick Turner.