Guy Lambert and Simon White are taking on the roles of joint deputy heads of planning and will report to John Lowery, the head of planning, who joined in February 2005.
Lowery said Grey had been working on improving the quality of its creative output since he was brought on board and that good planning would help to achieve this aim.
"Giving Guy and Simon these titles is part of our plan to boost the planning department, a key pillar in our effort to transform the agency," Lowery said. "High-quality planners improve the quality of our creativity."
Lambert joins Grey from Burkitt DDB, where he was the planning director and worked across a number of clients, including Nestle and John Lewis. Before Burkitt DDB, he was a planner at Lowe and Leagas Delaney and a partner at Sparkler, a media brand agency. During his time at those agencies, Lambert worked on a variety of accounts including Orange, the BBC, Interbrew, Tesco and General Motors.
Lambert said: "Grey's latest campaigns and awards show how the agency is changing. It's exciting. I want to be part of that and to help Grey carry on changing."
White has been promoted internally. He joined Grey in May 2002 as a planner and over the past four years has worked across many of the agency's clients, including Pringles, Fairy, AOL and Dairy Crest.