Cubitt took the unprecedented step of publicising its resignation of the SAB business following an emergency session of its eight-strong advisory board late last week.
The meeting, chaired by Cubitt board member and former Royal press attache Charles Anson was followed by a statement claiming the resignation reflected 'policy disagreements over international media relations activity'.
Cubitt founder Simon Brocklebank-Fowler refused to comment beyond that statement, but those close to the agency played down suggestions the resignation was linked to the appointment of Sue Clark as SAB's corporate affairs director.
The Cubitt board is understood to have developed strong links with Clark despite SAB's disputes with the agency. One industry source said those disputes 'predate her arrival by several months'.
Clark joined the group last month. Her appointment raised some eyebrows in the City since SABMiller already had a director of communications in Nick Chaloner.
Clark's role is wider than Chaloner's, encompassing his remits of PR and IR, as well as taking in internal comms, public affairs and CSR. She also took the seat on the company's executive committee that Chaloner held until her arrival.
Chaloner declined to comment as PRWeek went to press.
Cubitt was appointed by the world's second largest brewer in October 2001 after a pitch against incumbent Brunswick.
Clark said: 'Clearly, we now need a new corporate and financial agency.
We are considering a range of approaches to that problem.'