Mr. Berlin is United's global chairman-CEO, based in New York, where he is chairman of Berlin Cameron, but he has been spending a lot of time in London. Six of the nine remaining United agencies are based in Europe.
Move to micro-network
Ms. Walsh joined United's precursor, Red Cell, in 2004 when it was made up of 62 agencies. This number has since been cut to nine offices as WPP sought to create a competitor to agencies with micro-networks such as Bartle Bogle Hegarty, Wieden & Kennedy and Fallon Worldwide.
"You don't need two chief executives to run a micro-network," Ms. Walsh said. "It is right and proper that Andy stays as sole leader."
Executives familiar with United are again questioning WPP's commitment to the concept. Ms. Walsh's departure is deemed to be a cost-cutting exercise, implemented after the agency shed the Red Cell name and rebranded itself as Voluntarily United Group late last year.
Clearing up confusion
Agency chiefs around the network were said to have been confused about the roles of Mr. Berlin and Ms. Walsh. Now that only Mr. Berlin remains, the matter of whom to report to may be clarified.
Mr. Berlin said in a statement: "Amanda has been a great partner through extremely demanding times. United is now in robust shape. I've enjoyed working with Amanda immensely and count her as a friend. I regret we won't be working together but have been convinced this will prove best for all concerned."
Laurence Melman will continue as chief operating officer. Ms. Walsh leaves at the end of the month and has no immediate plans.