Howells was previously the managing director of BMPtvi, which was rebranded as OMDtvi in March. He took the role of interactive TV director as the operation passed from BMP to OMD.
Howells is leaving to launch his own interactive TV consultancy called Andrew Howells Associates. Toby Hack, the head of interactive media projects at OMDtvi, will take sole control of the agency.
An interactive specialist, Howells did not come from a media background and had not previously worked at a media agency. He launched BMPtvi after being a founder of the BMP new-media agency Bilco. Before this he worked at the video company Videologic.
Howells said: "The issue with being tagged OMD is that there is a limit to things you can work on. That's fine, but my work was done. OMDtvi has a few high-profile campaigns coming through and it's in safe hands."
BMPtvi was originally jointly backed by BMP, OMD and Tribal DDB, but control passed to OMD as the media buying and planning side of the business took off. BMPtvi was behind several pioneering interactive projects, including a joint venture with BBC MediaArc, and interactive TV firsts for clients including Rimmel and Reckitt Benckiser.
Paul Taylor, the chief executive of OMD UK, said: "Andrew was here working on the direct transfer of the business to OMD. Toby Hack is taking over now the transition process is over."