Agencies have been contacted by ISBA, which is acting as an intermediary in the process, ahead of a pitch for the business.
The move follows the brewer’s decision to launch new brand identities for Worthington’s and Caffrey’s. Molson Coors recently hired Landor Associates to develop new visual identities for both products.
Molson Coors has not backed either brand with recent advertising support and does not retain agencies for the beers.
Nathan Haigh, the ales brand director at Molson Coors, said: "With Caffrey's and Worthington's, we're looking to bring a new, fresh approach to the ales category from two of its best-known brands. As part of that, Molson Coors continually reviews its roster of marketing agencies so we always have the best match."
The appointed agency will be expected to build on the recent rebranding work. Worthington’s, which claims to be Britain's oldest ale, has introduced the line "Ales of character" on its cans. Caffrey's was redesigned to "re-engage a lost generation of ale drinkers" who have moved on to rival brands, according to Molson Coors. Its blue, silver and green cans were replaced with a dark green pack design to emphasise its Irish heritage.
Molson Coors also owns the Carling, Grolsch and Coors beer brands.
The brewer appointed VCCP Blue to the £7 million Carling ad account in June. VCCP also works on Coors Light, while Beattie McGuinness Bungay handles the Groslch account.