WITH the clingy, sexy, form-fitting clothing typical of summer, designers worldwide are jumping at the opportunity to use Lycra in their collections. The fibre was invented by a chemist from Du Pont 40 years ago and is now patented by the US-based company, but everyone from French haute couturiers to Asian manufacturers are wanting to infuse Lycra into fabrics used for their collections. More importantly, shoppers are looking for the Lycra hang-tag on clothes, convinced that it does make a difference to the overall look of the garment: skirts no longer cling to the backside, hemlines do not sag and there is no unsightly bunching up at the elbow. Once Lycra is blended in with a fabric - now anything from cotton to linen, silk to wool - the material takes on a new form and function. Lycra used to be associated with shiny spandex and polyester, but things have changed, and the fibre is now being used on the flowing yet form-fitting fabrics that are marking this summer's fashions. Today, Lycra can be found in everything from velvet and sequinned evening gowns to fun weekend leggings, oversized duster coats to neat and tailored executive suits. More recently, leading sports shoes manufacturers have been experimenting with Lycra. Largely due to the hugely successful ''Lycra Sensations'' marketing campaign, which was launched in Hongkong at the end of last year, fashion industry insiders have begun to catch on. Big-name retailers such as Joyce, Lane Crawford, Seibu, Marguerite Lee, Gottex and Jessica have the Lycra hang-tag on a number of garments, as do independent award-winning designers in the league of William Tang and Walter Ma. In Asia, Lycra is close to becoming the fashion sensation it already is in the US and Britain. In Hongkong, Singapore, Korea, Taiwan and Thailand, designers and manufacturers are beginning to wake up to the idea that if they want their clothes to sell, then the appearance of the Lycra tag is important. They are realising that in the more cost-conscious 1990s, quality counts more than the name-brand: consumers will happily pay more for something that will wear well and last longer, but are thinking twice about spending frivolously on a garment just because it has a designer label. ''We are working closely with retailers and manufacturers and having discussions with key brands in the run-up to a major promotional campaign,'' said Mr Kin Mak, regional marketing communications manager for Du Pont Asia Pacific. Mr Mak said the Lycra tag was an assurance of quality. Once mills agreed to use Lycra in their textiles, the fabrics were stringently tested before tags were issued, to ensure the correct strength of Lycra was used. Internationally, some of the world's biggest fashion names have jumped on the Lycra bandwagon. Where it was once the domain of an eclectic few like Jean Paul Gaultier, more contemporary designers such as Donna Karan, Calvin Klein and Liz Claiborne find they cannot do without it. ''Lycra basically opens up a whole new dimension in the philosophy of design. Even if you are talking about a casual, loose jacket, Lycra keeps the shape nicely,'' Mr Mak said. ''Clothes are no longer constricted, even if they are form-fitting. You can see and feel the difference, so fabrics containing Lycra give designers a lot more freedom in creating. ''We would like to see Lycra being developed on every level, but it should be consumer-driven,'' Mr Mak said. ''Just look at how times have changed compared to the 1980s: there is less and less ostentation and flashiness, and more emphasis on quality.