LBi and Crayon, the incumbents on the business, have been invited to repitch as part of a process that is expected to last six weeks. Agency.com, which handles online advertising for BT's broadband, mobile and business services, is unaffected by the review.
The account is understood to involve targeting business and consumer customers who use BT.com to manage their accounts.
The review, which is procurement-led, will include online ads, website design, technology and emerging media services. Sarah Mitchell, the procurement manager, marketing and brand for BT, is handling the process.
BT has recently stepped up its attempts to position itself as an IT and networking services company. Earlier this year, it bought the retail e-commerce service provider Fresca, with a view to strengthening its e-commerce and IT integration capabilities.
Fresca hosts and manages e-commerce services for more than 20 retailers, including Habitat and Whistles.
Last November, the company launched BT Fon, to create the world's largest Wi-Fi network. It allows members to access each other's internet connections via laptops and other portable devices.
BT Fon recently launched an online ad campaign, created by Albion, to encourage people to create the world's biggest Mexican wave by uploading videos of themselves.
A spokesman for BT said: "BT is keen to ensure we have the best design, development and production skills to help us further improve our growing portfolio of digital properties, products and services."