Richard Storey, currently the planning director, will take up the position of chief strategy officer with a brief to develop the agency on a global basis.
He will be replaced by Matt Willifer, who is moving to M&C from Heresy where he was also the planning director. Willifer will run the planning department as well as work on key clients in the UK. Before joining Heresy, he spent eight years at BMP DDB as a planner.
Storey said: "Matt brings the rigour of BMP training and the breadth of thinking of Heresy. He will complement and extend our discipline of brutally simple thinking."
The third promotion is Marcus Peffers, who becomes deputy managing director.
Previously the group account director, he will now take on a more strategic role with responsibility for launching and developing new business. Peffer becomes part of a global team that will work across the agency's international business.
Carrie Hindmarsh, the existing deputy managing director, will continue in her role but will focus more on the UK business.
Tim Duffy, the chief executive, said: "These changes are designed to upgrade the agency's offering, reward talent and take us to the next stage in our development."