The business, which includes advertising for Cathedral City cheese, Clover, Country Life, Utterly Butterly and Frijj shakes, has been held by John Ayling & Associates since 2003.
Other Dairy Crest brands include Wexford Chedder, Davidstow, St Hubert, Vitalite, Willow and Country Life milk.
The bulk of Country Life's media spend was on TV advertising in the 12 months to the end of February, with £9 million invested in the medium, according to Nielsen data.
Country Life attacked its rival butter brand Anchor in a new ad campaign launched this week. The print work, created by Grey London, features an image of the former Sex Pistol John Lydon with the strapline: "Anchor's from New Zealand."
Underneath the picture, the caption reads: "So?! I buy Country Life cos I think it tastes best."