LONDON, United Kingdom — Asos Plc, the U.K.'s largest online-only fashion retailer, said Chief Executive Officer Nick Robertson will step down, 15 years after he co-founded the business.

Robertson will remain with the company as a non-executive director, London-based Asos said in a statement Wednesday. His replacement as CEO will be Chief Operating Officer Nick Beighton.

Under Robertson, Asos has grown from a startup to become a leader in online fashion retailing with annual sales of about 1 billion pounds ($1.5 billion). The CEO, who was honored with the title Order of the British Empire in 2011 for his achievements in the world of clothing retailing, holds a stake in the company worth more than 200 million pounds.

“We are fortunate to have such an able successor for the CEO role,” Chairman Brian McBride said in the statement.

Beighton joined Asos in April 2009 as chief financial officer, becoming COO in October last year. Beighton’s successor as CFO, Helen Ashton, started at the company Tuesday.

Robertson is stepping down on a positive note. At the company’s last business update in July, Asos said it expects full-year sales to be at the higher end of its forecast range, which is 20 percent.

Asos shares fell 0.3 percent to 2,984 pence in London on Tuesday, trimming their gain this year to 16 percent. The stock was first sold to the public at 20 pence a share in October 2001, when the company was called As Seen on Screen and sold imitations of designer fashions worn by celebrities.

By Paul Jarvis; editors: Matthew Boyle, Thomas Mulier, Paul Jarvis.