Wigham will work across OMD UK and MG OMD to ensure its client spend with media owners works as efficiently and effectively as possible.
He will report to Steve Williams, the chief executive of OMD Group, and John Overend, the managing director of Omnicom Media Group's trading arm, OPera. His promotion follows the departure of OMD UK's Neil Johnston, the joint head of buying, in September 2011.
Wigham has been the head of investment at MG OMD since 2009. He joined OMD UK as a buying manager in 1998 and was promoted to deputy head of TV before switching to MG OMD to become its broadcast director in 2008.
Williams said: "Matthew is a super-talented guy who works in an intelligent and collaborative way."