Paul Bainsfair is set to team up with his former business partner John Sharkey, and plans to launch a digital advertising business.
The pair, who along with Dave Trott founded the ad agency Bainsfair Sharkey Trott in 1990, are thought to be working on the launch of what a source described as "a web-based company which will sell advertising".
Bainsfair confirmed he is "looking at a number of things with John", whom he last worked with nine years ago, but declined to go into more detail about the company.
Sharkey and Bainsfair are understood to be working with the Glasgow-based digital agency Dog Digital on ideas for the company, which is set to launch later in the year.
The venture comes four months after Bainsfair quit as the TBWA\London European chairman in the wake of a shake-up at the London office.
Earlier in the year, Perry Valkenburg was hired over Bainsfair for the role of European president and worldwide chief operating officer. Bainsfair's TBWA role will be covered by Tim Lindsay, who joins as the chief executive of TBWA Group UK.
Meanwhile, Sharkey has been working on a consultantcy basis with a number of his former clients.