The successful ad agency will be briefed to produce campaigns aimed at acquiring and cultivating a raft of new supporters, while at the same time retaining and developing its relationship with the donors it already has.
The incumbent, WWAV Rapp Collins, will not repitch for the business.
In September last year, the charity appointed DraftFCB to handle its advertising account, following a competitive pitch. In May, it appointed MediaCom to handle its £1.5 million media planning and buying account.
The move to appoint a DM agency comes as part of a drive to double the charity's fundraising revenues by mid-2009 in order to tackle overcrowded conditions at the hospital, which treats around 150,000 patients each year.