Senior consultant Wilson-Smith will leave in the coming weeks following a decade with the agency, which PRWeek revealed on Monday is also set to lose Sean Worth.
However Wilson-Smith, who declined to comment, is understood to be mulling over his options for the future and is not set to join Worth’s new consultancy.
Described by one source as having a "superb reputation in the City", Wilson-Smith was previously editor in chief of widely read financial industry publication Financial News and spent five years working as a reporter for the BBC’s The Money Programme.
Recent clients of Wilson-Smith have included former Financial Times editor Sir Richard Lambert, who is set to head a new banking standards review council.
Quiller, which is made up of ten consultants and covers public affairs as well as litigation and financial and corporate work, declined to comment.