After a succession of new business wins, it is believed OMD decided it was unable to invest the necessary time and commitment to vie for the business.
The four agencies will begin pitching for the media planning and buying business for Abbey National, Alliance & Leicester and Bradford & Bingley on 24-25 November.
This will be followed by an online auction process on 17 December, with a view to the financial group announcing the winning agency before Christmas.
Media Week revealed the Spanish group was reviewing its UK media planning and buying arrangements after a series of autumn acquisitions following turmoil in the UK financial market.
Based on Nielsen figures, the accounts were worth £42.5m in 2007, although this expected to be reduced closer to £30m in 2009, and it does not include the entire B&B business.
The decision also leaves OMD's new business team to focus on its head-to-head battle against Carat for Vodafone £57m account.