The two incumbents are going head to head in a winner-takes-all review. The review follows Coty's $800m acquisition of Unilever's global prestige fragrance business, Unilever Cosmetics International, in May last year.
OMD handles the £16m lion's share of Coty's UK cosmetics business, while Initiative oversees the £6m planning and buying for the former Unilever-owned brands.
The cosmetics business is divided into two divisions - Coty UK, which houses Coty's mass-market brands, and Coty Prestige, which includes those brands bought from Unilever.
The company's brands include Rimmel, fronted by Kate Moss, David and Victoria Beckham's "his and hers" fragrances, Intimately Beckham, Calvin Klein, Cerruti, Vera Wang, Davidoff and the Adidas cosmetics range.
Initiative handles 45% of Coty Prestige's UK media planning and buying. OMD looks after the remaining 55% and all of Coty UK. Coty's advertising is created in-house and by overseas agencies. Nobody from OMD, Initiative or Coty was available for comment.
Europe is Coty's biggest international market, accounting for half its global sales, which in 2005 were $1.6bn. Last year's Unilever deal has enabled Coty to branch out from its mass-market brands such as Davidoff and Adidas.
This month saw the launch of a major press ad campaign featuring David and Victoria Beckham promoting mass-market Intimately Beckham. The ad was created in-house and was shot by photographer Mikael Jansson.
It shows the couple embracing, with the former England captain holding his wife's rear. The ad has drawn accusations from the press that the image has been enhanced to make her rear look bigger.
Last year, Coty's Rimmel considered dropping supermodel Kate Moss from its advertising following allegations in the Daily Mirror that she had snorted cocaine.
This summer Coty signed a fragrance licensing deal with Kylie Minogue. The first product is expected to be rolled out in November. Coty is owned by Reckitt Benckiser.
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