The Brussels-based European Association of Communications Agencies (EACA) has published a 44-page report, called Auditing: Contract Compliance & Media Benchmarking – Rebuilding Trust.
It highlights the need to protect agencies’ data confidentiality, to draw up professional standards for auditors, and to avoid potential conflicts of interests.
"Trust between agencies, advertisers and auditors could be significantly improved by collectively addressing specific areas of potential concern," the EACA said.
The report, which interviewed dozens of people involved in the media supply chain over six months, recommends:
Bulletproof confidentiality guarantees: "More rigorous processes and procedures need to be put in place to safeguard the sensitive and valuable data provided by agencies to the diverse range of media auditors."
Consistent professional and evidenced standards: "More robust internal measures and controls need to be upheld, and evidence provided, by all media auditing businesses (e.g. accreditations, qualifications, independent verifications etc.)"
Zero conflicts of interest: "Certain standards need to be incorporated into the decision-making process when appointing independent media auditors, benchmarkers or advisers."
EACA is "seeking to pull together a collaborative, cross-industry working group" to resolve differences with advertisers, media auditors and others in the media industry.
It also recommends creating "best practice guidelines" and a "more binding, mutually agreed code of conduct".
The big six global agency groups, WPP, Omnicom Publicis Groupe, Interpublic, Dentsu and Havas, have been under intense scrutiny after a report by the US Association of National Advertisers into media agencies last year found "non-transparent" practices were pervasive.
Since then, advertisers are said to have clamped down on agencies around the world, although the agency groups denied any wrongdoing.
Advertisers use specialist media auditors and compliance auditors to monitor and check that agencies are adhering to their contracts.
However, agencies have privately raised fears that media auditors might misuse confidential data to inform clients and complained about a lack of independent regulation.
Media and compliance auditing firms are not required to be chartered accountants.
Dominic Lyle, EACA’s director general, said: "Media agencies view media auditing and benchmarking as a potentially positive way to demonstrate contractual compliance and prove delivery of strong media value to their clients.
"Nevertheless, for this process to work effectively, agencies need to be fully assured that the companies involved are able to operate as truly neutral arbiters, whilst upholding the highest professional standards.
"Today’s data and digital centric media marketplace, however, has inevitably led to greater caution as agencies now provide auditors with significant volumes of highly sensitive and confidential data. In addition, they are concerned about the potential conflicts of interest between specific divisions within some of the auditing companies.
"The bottom line is that agencies rightly expect these assessments to be conducted with full confidentiality, impartiality and professionalism."
Agencies often clash privately with media auditors. Group M, the media-buying arm of WPP, went public when it sued Firm Decisions, a subsidiary of Ebiquity, a media auditor, in London’s High Court last year over the alleged "misuse" of confidential documents.
Ebiquity denied wrongdoing and the two sides agreed to drop the case this year without a trial.