The combined account, which is held by Publicis, comprises the Kingsmill and Allinson ranges as well as the lower-spending Burgen, Sun Maid and Sunblest brands.
Allied Bakeries is approaching agencies through Yardley Greer - an intermediary owned by Simon Yardley and Virginia Greer, the pairing that once headed BMP's second-string operation BMP4. A longlist of six agencies has already been drawn up. This will eventually be shortened to three. The pitch, which will include Publicis, will take place during December and January.
An Allied Bakeries spokesman said: "After a long and successful relationship with Publicis, Allied Bakeries is to review its advertising business. The decision is a bid to ensure we maximise the future opportunity for Kingsmill, the UK's sixth-biggest grocery brand, and other brands in our portfolio."
The review does not affect the Allied Bakeries media account, which is held by ZenithOptimedia UK.
Allied Bakeries is the largest bakery in the UK. Its nearest rivals is British Bakeries, whose brands include Hovis, Mothers Pride and Warbutons.
The company uses the TV presenters Mel Giedroyc and Sue Perkins to promote the Kingsmill brand.
The sports presenter Gaby Logan was recently signed up to front Kingsmill's "Kit for Clubs" initiative - a scheme that enables customers to collect tokens and exchange them for free sports equipment for schools clubs. Logan has featured on all point-of-sale material and made a cameo appearance in a TV ad.