The agency has been tasked with developing the Style Advisor Loyalty Card, which is designed to increase the number of customers using the retailer's free in-store advisory service.
The style-advice service allows customers to make use of a special in-store suite, where they can discuss ideas while the advisor runs the purchases through the till and wraps them.
The launch will be supported by a campaign created in-house as well as an email drive handled by EHS Brann. The email activity will be timed to coincide with seasonal fashion ranges and tailored to individual Topshop customers' shopping habits.
The Arcadia-owned retailer has also hired EHS Brann Discovery to handle measurement and analysis of the scheme. Topshop aims to launch the card in November.
In April, Topshop went head-to-head with New Look when it launched its Kate Moss collection against New Look's Lily Allen range.