Starcom MediaVest Group will pitch for the business together with digital specialist I-Level. The collaboration will be called Smile. GroupM is also in the running under the group name M4C and Aegis Media's Carat will be pitching with sister agency Posterscope.
The winning agency group will take responsible for all of the COI's media buying from April 2010 on a four-year contract.
Pitches will be held in December and an announcement is expected to be made early in the New Year.
Previously the COI's buying account was split according to individual media.
The government departments and public sector bodies covered by the COI spent a total of £211m on media and £40m on online advertising during 2008/9.