OMG Digital will coordinate digital media buying globally to ensure that clients of Omnicom digital agencies OMD Worldwide and PHD Network get maximum negotiating leverage.
It will also invest in new initiatives, and has already begun to develop a proprietary media intelligence tool to track the way consumers interact with digital advertising.
Finnegan will report to Daryl Simm, chairman and CEO of Omnicom Media Group. The structure will see managing directors appointed in Europe, the Middle East and Africa, Asia Pacific and Latin America.
Omnicom said that the creation of the new unit would not affect the way clients of OMD and PHD received digital media services.
Simm said: "The investments we're making in OMG Digital initiatives will provide all our clients with unrivalled insights into consumer behaviour and help maximise their ROI."