Earlier this year, the Trader Media Group outfit decided to bring its online advertising in-house - having previously outsourced some of its operations to AdLink.
Jo Betts, online account manager at Manning Gottlieb OMD who works on the Nissan UK account, said: "The way that Auto Trader handles our account and reports results has a major impact on the level of advertising we have placed with them in 2008."
The group has now switched from aligning its online sales operation along the three verticals of automotive, finance and insurance, and lifestyle to housing three agency-focused hubs, covering GroupM, Omnicom and Aegis.
The GroupM hub is headed by Ryan Carter, online sales manager; the Omnicom group is led by Alanna Tyminski and the Aegis hub is headed by Al Mottram.
Carter said the move will make Auto Trader's sales operation more efficient and allow it to "cover business a lot better".
Auto Trader claims to have posted a 35% growth in display ad revenue for the first six months of 2008.
Earlier this year, Auto Trader unveiled plans to broaden its advertiser base with a title relaunch and £15m ad campaign to change its brand perception.
The motoring title's relaunch included a new-look front cover, redesigned logo, changes to editorial content, revamping of the Auto Trader website and the launch of five new supplements.
Most of Auto Trader's regional editions suffered drops in circulation, according to the last ABC figures, released in February.
Auto Trader North West had a year-on-year circulation fall of 14.2% from 33,094 to 28,396 copies, while its Midlands title suffered a similar year-on-year decline.