The firm, which owns the Smirnoff, Baileys and Guinness brands, is reviewing direct mail, digital and CRM activity.
The direct and digital agencies that are understood to be affected include Tullo Marshall Warren (TMW), AKQA, Agency Republic and Chemistry Communications.
A spokeswoman for Diageo said: "The review is to ensure we have efficient, creative, first-class business practices and partners in place."
TMW works across several brands. AKQA handles Smir-noff, and Agency Republic and Chemistry work on Baileys.
Roster creative agencies include Abbott Mead Vickers BBDO, Adam & Eve and JWT.
Diageo spent £24.5m on advertising in 2009, according to Nielsen. This was down 27% on the £33.9m spent in 2008.
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