The pair resigned last week. A statement from the agency said that they left to "explore new creative opportunities".
Responsibility for the creative department will pass to its two lead creative teams, Rebecca Rae and Leigh Roberts, and Mark Buckingham and David Brown. The lead teams were put in place last year to allow management responsibility to be shared among the most senior creatives.
Kershaw and Keevill were made creative directors of Craik Jones in 1998.
They joined the agency in 1992 from Ogilvy & Mather Direct and presided over one of the most awarded creative departments in direct marketing.
Fiona Scott, the managing director at Craik Jones, said: "Simon and Phil have produced some outstanding work. We have enjoyed working with them enormously but 11 years is a long time in one place. And they are now keen to seek new creative challenges. We are very sorry to see them go, but wish them every success in the future."
Kershaw refused to comment as Campaign went to press.
Pamela Craik and Chris Jones, the founding creatives of the agency who hired Kershaw and Keevill, are no longer involved in the day-to-day running of the agency.
Since its acquisition by Abbott Mead Vickers in 1997, which led to subsequent ownership by Omnicom, the five founders of Craik Jones have completed their earnouts. Pamela Craik and Chris Jones, the founding creatives of the agency who hired Kershaw and Keevill, are no longer involved in the day-to-day running of the agency.