Long, who has worked as a non-executive adviser to Naked for the past 18 months, takes on the full-time role as Naked attempts to expand its global group operations.
He was previously the chief executive of Euro RSCG London and Partners BDDH. He left Euro in March 2004 following the arrival of Ben Langdon as the agency's chairman.
Long will be based in London and will work with Naked's four partners - Will Collin, John Harlow, Jon Wilkins and Ivan Pollard - on running Naked's 15 ventures in six markets. He will also focus on the UK market, assisting the recently installed UK management team of Niku Banaie, Jo Pearce and Geoff Gray.
Harlow said: "The business is diverse and it's growing quickly. We're working with some big global clients and the dynamics are shifting from those of a cottage industry to something bigger. We wanted to add some strength to our senior business strategy."
Long steps up to the chief executive role after working with Naked on projects such as its launches in London and New York.
He said: "The work Naked does is interesting and my role is to extract the best commercial value from that."
Comment, page 44.