Chase, the US consumer and commercial banking division of JPMorgan, has called in auditors to examine its relationship with Publicis Groupe media agency ZenithOptimedia, the company that buys advertising on its behalf.

A source told Business Insider the decision to call in auditors around two weeks ago is a direct response to the high-profile report published earlier this month by the Association of National Advertisers (ANA), which alleged that volume discount rebates and other non-transparent business practices are “pervasive” in the US media ad-buying ecosystem.

Read the full Business Insider article here.