The move marks a step change for the retailer, which has traditionally used a variety of agencies to handle its advertising, and indicates the retailer is looking to create a greater consistency across its brand image.
Mother was appointed after Selfridges approached a number of creative agencies about its advertising in October. The brand is now looking to move from its positioning as a retailer to that of a leisure and experience brand.
Selfridges, which is expanding across the UK with a store in Manchester, another planned for Birmingham next year and a fourth planned for Glasgow in 2007, is also considering European expansion.
This planned expansion has been behind Selfridges' decision to leave its project-basis advertising appointments in favour of consolidating into one shop. Karmarama created Selfridges' award-winning Tokyo Life campaign with Naked Communications, while Dinosaur was briefed to launch its Manchester store.
Media will continue to be handled by Starcom Motive.
Stef Calcraft of Mother said: "Selfridges has been a phenomenon in recent years. The team there are even more ambitious for the future, which is why we want to work with them to take things on to the next level."
James Bidwell, the director of marketing at Selfridges, said: "We have very big plans for the brand and the business over the next five years and we need a like-minded partner to bring these to fruition."