Victoria Beckham is a woman who wears many hats - style icon, singer, wife, mother - but one thing she has never called herself is a designer. When she launched her denim line dVb last July, there wasn't much hype, but fast forward to December and Women's Wear Daily were reporting that her eponymous collection of dresses sold out at New York's Bergdorf Goodman almost immediately, as it had done in London a month earlier. This is not surprising because Beckham's brand is one of many celebrity lines that have become international successes overnight. Look at Sean John, the urban, hip hop fashion line of rap star Sean Combs. While his line does not push boundaries or offer anything exceptionally creative, it clicks with a market looking for well-made clothes with street credibility. Gwen Stefani's line, Lamb, is another case in point. Stefani used her fashion icon status to launch a clothing that combined glamour with rock and roll. Andre 3000, the hip hop star and designer of the label Benjamin Bixby, has also capitalised on his name to launch a collection of modern preppy clothes in the vein of Ralph Lauren and Brooks Brothers, but with an edge. This month, he is featured in GQ magazine as one of the best new designers in the America. 'Sean John is a successful line that appeals to a target market because he signifies a great lifestyle and success to his constituents,' explains Milton Pedraza, CEO of the Luxury Institute, a research body consulted by luxury brands on the buying patterns of high-net-worth consumers. 'Gwen Stefani is successful because her range looks like herself,' adds David Wolfe, creative director of New York-based trend forecasting agency Doneger Group. 'I think that celebrity ranges will sell if they are priced well and designed with some integrity to the star's own image.' With our obsession over celebrities and what they wear, it's only logical that celebrity lines will thrive in the fashion industry. After all, the celebrities themselves are the best advertisement for a product. 'The appeal is that the celebrity is admired and respected, and it reflects the lifestyle of the celebrity in an authentic way,' says Pedraza. 'The cult of the celebrity has meant that many consumers want to mimic their favourite star's style, and buying into a clothing line is an easy way to achieve their idol's look. There will always be a market for these designer clothing lines as long as people are interested in celebrities and their style,' adds Holli Rogers, buying director of online luxury retailer Net-a-Porter.com. Actresses Mary-Kate and Ashley Olsen, founders of fashion lines The Row and Elizabeth and James, are probably the most obvious example of this. As young women whose fashion style is copied by almost every girl in America, it was only natural for them to parlay their knowledge of how to put clothes together into a business. But unlike other celebrities turned designers, these two have gained respect from the industry while turning heads for their cool and fast forward designs. 'The Olsens have established themselves as credible designers with a strong aesthetic and choosing to use a brand name without incorporating their own says a lot about what they are trying to achieve,' says Rogers. 'Last year, we picked up their contemporary label, Elizabeth and James, which has proven to be consistently popular with our customers. We have bought the brand again for spring and must-haves include the cotton boyfriend shirt and the ruched sleeve, single breasted blazer.' The Olsens' critical and commercial success, it seems, lies in their own cachet in the fashion industry - they may not be trained designers but they love, live and breathe fashion. 'I believe celebrity lines can be successful if the icon is relevant to a target market. They must deliver great quality, design and great customer service, just like any designer,' says Pedraza. That's not to say that every celebrity-launched line will be met with the same enthusiasm as Beckham's or the Olsens'. Heidi Montag and Lauren Conrad of The Hills fame both launched clothing lines that tanked, while Beyonce's House of Dereon is still struggling to make a connection with a target audience. Justin Timberlake's William Rast is getting a lot of publicity mainly because of Timberlake's performances at the label's fashion shows, but whether it is selling has yet to be determined. JC Report, an online publication that analyses trends and consumer behavioural patterns, reported that Jessica Simpson refused to be photographed wearing her own clothing line. 'Celebrity clothing lines are just so last century,' says Chris Sanderson, co-founder and creative director of international trends consultancy Future Laboratory. 'Who really cares about celebrities any more? By definition, celebrities are people who are famous for being famous. Their talent lies in not being good at anything in particular. They are not credible and will never have the same credibility as a clothing designer whose skill, passion and craft revolves around making clothes that make people happy, not making clothes to simply make a celebrity richer.' Experts also point out that with the world in recession, customers will become more discerning when it comes to what they spend. This also means buying clothes that will last and, more importantly, that have design integrity - a quality that not many celebrity lines can boast. 'In the face of a global recession, the name of a talentless wonder promoted by money-men is deeply out of tune with a world that is looking for inspiration, talent and answers,' says Sanderson. And if talented designers such as Peter Som and Narciso Rodriguez are struggling with their label's financial standing, what will be the success ratio of a clothing line from, say, Jessica Simpson? Only time will tell.