Founder of British online retailer ASOS steps down as CEO

* Founder Nick Robertson steps down as CEO

* To stay on as non-executive director

* COO Nick Beighton becomes CEO

* Shares (Berlin: DI6.BE - news) recoup early losses (Adds detail, background, updates shares)

By James Davey

LONDON, Sept 2 (Reuters) - Nick Robertson, the founder of British online fashion retailer ASOS (LSE: ASC.L - news) , has quit as chief executive after 15 years in which he transformed the Internet start-up into a retail powerhouse with millions of fans around the world.

ASOS, whose fast fashion is popular with Internet savvy twentysomethings as well as celebrities such as singer Rita Ora, said on Wednesday that Nick Beighton, its chief operating officer, would take over the top job with immediate effect.

Robertson, who started the business in 2000, made it one of the retail success stories of the original dot-com boom. But competition has increased as new online rivals have sprung up and established retailers now also sell via the web.

ASOS had a tough 2014 when it issued three profit warnings, hurt by the intensifying competition, a step-up in investment, the negative impact of exchange rates and a fire at its main warehouse. But its shares have risen 17 percent so far in 2015 as trading has recovered.

Last month, the company raised its full-year profit guidance after a strong third quarter in which its global active customer base grew to 9.7 million.

Uncertainty over whether the loss of Robertson could hinder growth contributed to a fall of over 5 percent in ASOS shares early on Wednesday.

But most analysts viewed the succession as orderly, noting the recent appointment of Helen Ashton as chief financial officer had freed Beighton to focus on operational matters.

They were also relaxed about the changes as Robertson, 48, is staying on as a non-executive director.

ASOS shares rebounded and were up 1 percent at 30.13 pounds ($46.13) by 12:18 GMT.

"It (Other OTC: ITGL - news) is not a big surprise, as he (Robertson) has been a little disengaged from the business recently," independent retail analyst Nick Bubb said. "Beighton has been well groomed as his successor."

Bubb noted, however, that investors would wonder about possible share sales, given Robertson's 8.4 percent stake in the group, worth about 212 million pounds.

Robertson declined to comment when contacted by Reuters.

SUCCESS STORY

Robertson, a former advertising executive and great-grandson of tailor Austin Reed, started the-then As Seen on Screen with Quentin Griffiths and floated it on London's Alternative Investment Market at 20 pence in 2001.

When the Internet bubble burst this led to the spectacular failure of several web-based companies, but ASOS went from strength to strength as Robertson pushed it into new countries, expanded its offer of own-brand and branded products to more than 80,000 and was quick to exploit the benefits of social media.

ASOS became the big success story of the British retail scene. The shares hit a high of 71.95 pounds in February 2014, giving it a market capitalisation of 6 billion pounds before the first of last year's profit warnings.

The company is now valued at 2.53 billion pounds or more than two-and-a-half times the value of department store Debenhams (Other OTC: DBHSF - news) .

Beighton, 47, joined ASOS in 2009 as finance chief stepping up to COO in October. He was widely regarded by analysts as the heir apparent.

"We do not anticipate any sudden change in strategic direction," analysts at Liberum said, retaining their "hold" stance. "ASOS clearly has momentum in most of its key regions. We remain wary of the high rating but the market appears willing to accept this as long as the sales growth ... continues."

Despite coming off historic highs, ASOS remains highly rated, trading at 68.6 times analysts' earnings forecasts, according to Reuters data. That compares with 34.5 times and 24.4 times for the world's top two clothing retailers, Inditex (Amsterdam: IT6.AS - news) and H&M respectively. ($1 = 0.6532 pounds) (Editing by Kate Holton and Jane Merriman)