The bank is speaking to roster and non-roster agencies about reducing costs.
RBS uses five agencies at present. Joshua, Red Tag Marketing and Miller Bainbridge work on both the NatWest and RBS rosters.
In addition, Tequila\Manchester works on RBS and Lida, M&C Saatchi's DM agency handles NatWest's retail banking business. It is understood to want to reduce this number to two agencies.
The bank's procurement department has briefed the roster agencies to prepare for a review, asking them for revisions of their rates and how they will structure teams accordingly. It has also briefed two non-roster agencies to provide their suggestions.
The consolidation is part of an ongoing review of RBS's rosters. It follows a pitch last year for the NatWest retail banking business, when Lida replaced Craik Jones Watson Mitchell Voelkel.
Draft London, which handles direct marketing for RBS's Mint brand, is not affected by the review.