The announcement comes just a month after Howell denied he was planning to quit, following talks about the sale of the advertising agency he helped found, HHCL & Partners, to WPP Group.
In August, Howell told 北京赛车pk10 magazine: "I understand why people would ask what happens to me if HHCL joins a network. But HHCL isn't my main job any more and I want to see it sorted internationally and to help the development of Chime when the market hopefully begins growing again next year."
Chime today confirmed today that it is in discussions to make HHCL part of Red Cell, WPP Group's fourth advertising network. HHCL has struggled over the past 12 months in the face of major client losses including online bank Egg and Tango.
The addition of HHCL to WPP's Red Cell network would give it a creative powerhouse in London. WPP recently added French creative agency Les Ouvriers du Paradis and last year it acquired Berlin Cameron in New York.
Howell will be replaced by Chris Satterthwaite, currently group managing director of Chime's UK businesses. Satterthwaite joined HHCL in 1993 after 10 years at sales promotion agency IMP, the last three as chief executive.
His departure is the second high-profile departure from the Chime board this year. In June, business development director Robin Price also resigned. Price was another founder, alongside Howell, of Howell Henry Chaldecott Lury, which launched in 1987.
In a statement, Chime said: "We are announcing today the resignation of Rupert Howell as joint chief executive. He will leave the board in November this year as he has decided it is time for him to start a new business. We take this opportunity to thank Rupert for his contribution over the last five years and wish him well in the future."
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