Kemp, who co-founded The Marketing Store in 1986, will now join the RPM board and work with senior management at the agency's designated groups to help align them with RPM's overall business strategy.
He resigned as global chief executive of The Marketing Store in November 2006 to be replaced by David Bender, and is currently chairman of the Marketing Communication Consultants Association.
Since leaving The Marketing Store, Kemp has offered financial backing and mentoring to other former Marketing Store staff, and is understood to have been in negotiations with a number of agencies about non-executive directorships.
In a statement, RPM said: "Kemp's role will focus on working with the board and existing leadership team in delivering against the ambitious strategy for the RPM Group."
Hugh Robertson, managing partner at RPM, said: "We have looked at our strategy for the next three years and identified how best to ensure experiential stays at the forefront of marketing.
"We feel that with his experience in marketing as a whole, and particularly with The Marketing Store, combined with his business gravitas, ethics and values, Graham is an excellent addition to the management team."