Paul Taaffe has quit his role as global CEO of Hill & Knowlton, after 18 years with the WPP agency.

Taaffe, who became global CEO in 2002, becomes the third long-term veteran of the agency to resign within a week, following the merger between H&K and sister WPP public affairs agency Public Strategies (PSI) in November 2010.

That merger installed PSI founder and chairman Jack Martin as global executive chairman of Hill & Knowlton; Martin now takes on global CEO duties with immediate effect.

“I want to thank Paul Taaffe for his more than 18 years at H&K,” said Martin. “During the past eight years as chair and chief executive, Paul contributed significantly to its continued success and imprint as a global leader in size, geographic reach and profitability. In addition, he has contributed significantly to the advancement of the communications industry.”

“I’m excited that he has agreed to serve as a senior counselor to me and the firm for the next several months as we make this transition, as I know we can all benefit from his insights and wisdom,” added Martin.

Taaffe joined H&K as UK chief executive in 1992, becoming EMEA president in 1994 and worldwide CEO in 1998, before moving to New York in 2002.

Earlier this week, it was revealed that H&K US chairman Marylee Sachs, and global CMO Tony Burgess-Webb were also leaving the agency.