The review is statutory and will be led by John Scott, the former Burger King marketing director who was hired in February 2003 as the Post Office's head of communications.
The Haystack Group will handle the pitch, which is set to begin by the end of the year. It is thought that a decision will be made by spring 2006.
Publicis and Joshua were appointed to the account in the previous statutory review that took place in 2001.
The chosen agency will be expected to produce numerous TV campaigns as the Post Office spends around £10 million a year on the medium.
Its most recent work focused on its Home Phone service as the Post Office strives to hit a target of one million new customers by 2010, 5 per cent of BT's residential business.
The review may also bring an end to the company's current campaign that uses animated ants, which was created to show how the Post Office's over-the-counter services make customers' lives easier.
The Royal Mail is also set to review its £40 million media planning and buying account out of Carat in a statutory review planned for autumn this year.
Most of the Royal Mail's advertising is held by Abbott Mead Vickers BBDO, which will be unaffected by the reviews.