Rapier triumphed following a four-way shoot-out against Propaganda and the incumbents, Tullo Marshall Warren and Partners Andrews Aldridge.
The agency has been charged with using Lloyds TSB's new positioning "for the journey", developed by its above-the-line agency, Rainey Kelly Campbell Roalfe/Y&R, to help drive customer engagement across its entire range of services.
The win leaves Rapier with a potential conflict: the agency already handles direct marketing for the AA's car insurance services.
Until now, Lloyds has used several agencies to handle its below-the-line communications. The consolidation will come as a particular blow to TMW, which handled a large part of Lloyds' DM business.
Nigel Gilbert, the group marketing director for Lloyds TSB, said: "While TMW and PAA have done a great job, as well as the other agencies we use across the business, we wanted to achieve fewer and better relationships with our agencies in order to be fair and get the best from them.
"Although we saw some very good presentations, particularly from PAA and TMW, Rapier's presentation was really outstanding. It was bold and had excellent customer insight, as well as a good understanding of our brand."