Ralston-Good will drive innovation across OMG UK’s agencies and specialist services, including OMD UK, Manning Gottlieb OMD, M2M and PHD.
She said: "We should have products that have a role for the agency in terms of creative alongside the tech. Too often, agencies just jump into bed with a tech partner."
Ralston-Good will report to Philippa Brown, the chief executive of OMG UK, and Daren Rubins, the chief executive of PHD UK.
She joined PHD in 2011 as managing director, arriving from Naked Communications where she had worked in the same role.