WPP criticises Publicis’ Epsilon for poor ad quality and transparency

WPP has publicly levelled serious allegations against rival Publicis Groupe, claiming that its Epsilon-run supply-side platform (SSP) is contributing low-quality inventory to the digital advertising ecosystem. The accusations were outlined in a client-facing intelligence report released by WPP Media and mark a rare instance of a holding company directly calling out a competitor by name.

The document criticises Epsilon’s Conversant SSP for underperforming on key advertising metrics such as viewability and user engagement. It also raises alarms over the prevalence of “made-for-advertising” (MFA) websites within Epsilon’s supply chain, as well as a lack of transparency in inventory sourcing.

According to media reports, WPP CEO Mark Read has been privately raising concerns with clients for over a year regarding the quality of inventory delivered via Epsilon. The intelligence report, shared internally with WPP client leads in late May, encouraged teams to use the findings in conversations with brand partners.

WPP’s internal analysis is based on a programmatic buying test conducted on 19–20 May using its own media spend. Of the 500,000 impressions purchased, 26 per cent reportedly came from MFA sites, webpages designed to generate maximum ad revenue through high ad density and frequent refreshes. Additionally, 25 per cent of impressions originated from a retail site within Publicis’ CitrusAd media network, but achieved a viewability rate of just 2 per cent, according to the report.

The public disclosure marks an escalation in the long-running but largely private competition between the two advertising giants. WPP’s move highlights growing tensions in the digital media supply chain, where advertisers are increasingly demanding higher-quality placements and greater transparency in programmatic buying.

The timing of the offensive is notable. WPP has been under pressure in recent quarters, reporting lagging organic growth and bracing for disruption from a proposed merger between Omnicom and Interpublic Group (IPG). CEO Mark Read, who is set to step down later this year, is navigating the group through a period of strategic uncertainty.

Meanwhile, Publicis continues to make gains, having recently won Coca-Cola’s North America media business from WPP. It is also reported to have secured Mars’ global media account, further intensifying competitive pressures.

Neither Publicis nor Epsilon has issued a formal response to the WPP report at the time of publication.