Busk will take on the role in February, reporting to the agency's founding partners, Jonathan Trimble, Matt Keon and Tim Millar.
Trimble will now, in turn, assume the position of chief executive.
Busk, who has worked at DDB since 1996, is charged with developing and overseeing the agency's existing client base, which includes Nationwide, LoveFilm and Virgin Media.
He will also be responsible for the day-to-day running of 18 Feet & Rising alongside Rob Ward, the head of strategy who joined the shop from Bartle Bogle Hegarty in August last year.
Since joining DDB as a graduate trainee, Busk has risen to the head of account management, also running the Volkswagen business for ten years and overseeing accounts including Marmite and Budweiser.
Keon said: "If there was a Gunn Report for account handlers, Jon would have topped it as much as DDB has."
Trimble said: "Jon has an unmatched creative pedigree. An uncompromising taskmaster, he puts the work in the spotlight, not himself. It was a simple decision."
Busk said: "DDB is a timelessly brilliant creative agency, so the choice to leave was hard. It took something very special to catch my eye."