The agency will take responsibility for all Audi's technical web design and build, with particular focus on redesigning Audi's UK website.
The agency will work alongside Bartle Bogle Hegarty, Audi's lead creative agency, which will continue to produce online advertising.
Audi moved its digital advertising account into BBH, which also handles its above-the-line, DM and CRM business, in November last year. The move marks the end of Audi's relationship with GT.
The appointment of a digital agency to revamp Audi's online presence comes after Volkswagen, Audi's parent, reported a poor performance in the final quarter of 2008.
Although the company posted a 3 per cent rise in operating profit to EUR6.33 billion in its preliminary full-year results for 2008, the car manufacturer suffered a 25 per cent fall in its operating profit in the final quarter of 2008.