The direct marketing responsibilities will include mail, email and direct response advertising while the branding services required include brand design, positioning and insight.
The current incumbent on the Post Office's direct marketing account is DraftFCB, which was appointed to the roster in 2006.
The review is being led by Gary Hockey-Morley, marketing director for the Post Office since September 2006.
The Post Office wants to develop and exploit its customer database through both acquisition and customer relationship management as it attempts to "migrate the business from product focus to customer centric".
The tender will also focus on how the Post Office can best develop its media to maximise customer response/ROI through direct response media, with a particular emphasis on press, door drops and digital advertising.
Mother handles the Post Office's ad account, having won the £12m business in March 2007 after a pitch against DDB London and Grey.