Worthington will oversee the design division following a restructure at Media Square, which sees it split into three operating divisions. The other two are advertising and PR, headed by Philip Gregory, and marketing, headed by Mike Spicer.
The design agencies owned by Media Square are Coutts, Homes & Marchant, and Lloyd Northover. Worthington's brief is to grow these brands and foster a culture that promotes collaboration.
Worthington is consultant curator to the new London Transport Museum, which opens to the public in the next few weeks, and is also a consultant to the Sector Skills Council for creative and cultural industries.
Roger Parry, executive chairman of Media Square, said: "His knowledge of the design industry and the strategic use of design, coupled with his skills as a practitioner and as a successful manager, will be a real asset to the group."