The former commercial director at Initiative will replace David Connolly, who leaves next week after two-and-a-half years at Ofcom.
Connolly oversaw three TV trading seasons in the role, ensuring that ITV dealt fairly with advertisers and agencies.
He also ensured that ITV abided by the CRR's terms, which was a precondition of the merger between Carlton and Granada.
Ditcham was a broadcast director at Initiative and a launch director of TV station Rapture. He left the agency in June following a restructure.