The successful agency will function as an ideas shop to stimulate fresh thinking alongside St Luke's and Abbott Mead Vickers BBDO. The review has been overseen by the AAR.
Catherine Kehoe, head of marketing communications at BT Retail, said the company was looking for an agency that could come up with ideas and execute them at short notice. She added the third shop would have a flexible relationship with its existing agencies, creating work across its product portfolio.
Pitches take place in mid-March with a decision due in April.
BT Retail is preparing to re-enter the consumer mobile space later this year as a virtual operator. Last week, it struck a deal to lease network capacity from T-Mobile.
The telecoms giant hived off its BT Cellnet operation in early 2002 in a bid to cut its then-crippling debt.
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