WPP has inadvertently made public detailed spending information for some of the world’s biggest advertisers after submitting internal documents as evidence in a legal dispute with a former executive in the United States.

The court filing, now accessible through public records, reveals more than $9 billion in annual advertising expenditure across clients including Google, Coca-Cola, Unilever, Ford, JPMorgan, Shell, Adidas and Cartier. The material includes breakdowns of media spending by platform, agency-level revenue data, staffing costs and profit-and-loss information that agencies typically guard as highly confidential.

The disclosure stems from WPP’s defence against a $100 million claim brought by Richard Foster, who spent 17 years at the company before being dismissed last summer. Foster previously headed a division within WPP Media, the group’s media-buying operation formerly known as GroupM.

The Whistleblower allegation

Foster alleges he was terminated for raising internal concerns that WPP retained undisclosed rebates and discounts secured through media purchases rather than passing the full value to clients. His claim characterises this as improper retention of client funds.

To counter the whistleblower assertion, WPP filed a 35-page document that Foster had prepared in December 2024. The company argues the report was actually a business proposal focused on establishing a new entertainment unit, not a complaint about wrongdoing. WPP characterises Foster as a “disgruntled former employee” seeking additional severance and publicity.

The company maintains that its media-buying operations undergo routine audits and that no rebate handling has ever been deemed improper by clients or regulators.

What the filing reveals

The document contains commercially sensitive intelligence that holding companies typically protect fiercely. A table listing WPP Media’s top 20 clients in 2023 shows their marketing expenditures in granular detail.

Google advertising alone accounts for nearly $5 billion across WPP clients. Ford spent approximately $299 million on Google placements through WPP agencies. Unilever allocated around $194 million. Adidas contributed roughly $101 million.

The filing breaks down spending by platform and provides a detailed look at how individual WPP units perform financially. It reveals staffing costs, revenue per agency, and profitability metrics that would normally be considered competitive intelligence.

Foster’s document also alleged that WPP generates approximately $1 billion annually in profit from “non-product-related income”, including rebate-linked arrangements, with growth targets of 15 per cent.

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Industry reaction

Ivan Fernandes, a former WPP executive who now advises rival groups including Publicis, described the filing as “commercially significant” when speaking to The Times. He noted the material amounts to internal competitive intelligence rather than typical court documentation.

The exposure creates potential strategic implications. Competitors gain visibility into WPP’s client relationships, spending patterns, and operational economics. Clients may question why their confidential spending data is now accessible through public court records. Prospective clients might reconsider whether WPP adequately protects commercially sensitive information.

The legal context

WPP has accused Foster of attempting to “extort” a larger payout by threatening to publicise allegations. Foster’s legal team, led by Bill Brewer of Brewer, Attorneys & Counsellors, rejects that characterisation, saying WPP’s claim lacks evidentiary support.

The case remains ongoing ina  US court. WPP, led by chief executive Cindy Rose since 2024, declined to comment on the matter.

The broader rebate question

Foster’s underlying allegation touches on a persistent tension in media buying. Agencies negotiate rates with media platforms and publishers. They secure volume discounts, preferential placement, and various financial arrangements. The question of how much value flows back to clients versus how much agencies retain has long been a topic of debate.

Transparency agreements and client contracts typically outline the procedures for handling rebates and discounts. Major advertisers often conduct audits to verify they’re receiving the negotiated value. Industry bodies have established guidelines around disclosure.

However, the complexity of modern media buying, involving programmatic advertising, data licensing, technology fees, and various service bundles, creates grey areas. What constitutes a rebate versus a legitimate agency service fee isn’t always clear-cut.

Foster’s claim suggests WPP’s practices in this area merit scrutiny. WPP’s defence suggests Foster’s characterisation misrepresents standard business operations. The court will ultimately determine which position holds merit.

What this means for holding companies

The incident highlights risks inherent in legal proceedings. Companies submit evidence to defend their positions. That evidence enters the public record. Confidential business information becomes accessible to anyone who requests court filings.

WPP presumably weighed the competitive damage of disclosing client data against the legal necessity of refuting Foster’s claims. The company apparently concluded that allowing the whistleblower allegation to stand unchallenged posed a greater risk than exposing the commercial information.

Whether that calculation proves correct depends partly on the client’s reaction. If major advertisers view the disclosure as unavoidable collateral damage from defending against baseless claims, WPP’s relationships may remain intact. If clients see it as careless handling of their confidential data, the competitive damage could be substantial.

For other holding companies, the case serves as a warning about litigation strategy. The pressure to vigorously defend against claims must be balanced against the risk of publicly exposing information that provides competitors with strategic intelligence.

The disclosure comes as WPP navigates a challenging market environment. Holding companies face pressure from consultancies, in-housing by clients, and platform expansion by technology companies. Organic growth has been difficult to achieve. Cost discipline has become paramount.

In this context, the public exposure of detailed client spending, agency economics, and operational metrics creates additional competitive pressure. Rivals can use the information to target WPP clients with more informed pitches. They understand pricing, service delivery models, and profitability expectations in ways that would normally take years of market intelligence to accumulate.

The case continues. More filings may bring additional disclosures. For now, the advertising industry has unprecedented visibility into how one of its largest holding companies operates, what its major clients spend, and how profitable those relationships are.

Whether this transparency ultimately benefits the market or simply damages one player whilst providing a competitive advantage to others remains to be seen.