Post Office head of communications John Scott is heading the review, which is being managed by The Haystack Group. Pitches will take place later this year, with a decision due by next spring.
The two agencies were appointed more than four years ago with a brief to sustain and build the Royal Mail division's brand. The review could mark the end of its current brand campaign, which features animated ants.
The characters have been used to sell the Post Office's over-the-counter services since last year. The division spends about £10m on TV advertising, most recently focusing on the HomePhone service. The Post Office is striving to meet a target of 1m customers within five years, taking 5% of BT's residential business.
The majority of the Royal Mail's advertising is handled by Abbott Mead Vickers BBDO, which is unaffected by the statutory review.
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