The move will be a blow to PHD, which has handled the planning side of the account since 2005.
Sources close to the process said that talks were ongoing between Vizeum and BMW but that the car company plans to consolidate the business to make efficiencies.
The consolidation into Vizeum, which handles buying for BMW and sister brand Mini, will spell the end of the relationship between PHD and BMW Group.
Last year, PHD Rocket lost the Mini planning account when it was moved in-house.
Digital buying for BMW and Mini will remain with Zed Media.
The consolidation is expected to follow an internal review at the car-maker, led by the managing director, Richard Hudson.