Murray Dudgeon, currently chief operating officer at Universal McCann, will take on the role until a replacement is found.
Michael Roth, chairman and chief executive for Interpublic, said: “Marie-José has made tremendous contributions to Initiative over the years.
“Her talents and vision have helped Initiative grow and develop in ways that have benefited many of our key clients.
“We wish her well in her future endeavours and are working together to determine how best to tap into her considerable expertise going forward.”
Forissier will be replaced by Initiative chief executive Alex Gerster.
The move comes as Interpublic faces the loss of the General Motors dealership account in the US, worth around £1.5bn and on back of losing the mammoth Unilever account, which switched from Initiative to WPP’s MindShare last year, and Universal McCann’s loss of its part of the Nestle global media account.
However, Universal McCann recently won the high-profile £150m global Intel account, after the network retained the £400m General Motors European account.
By Kevin May