A British advertising conglomerate has helped the oil companies ExxonMobil, Chevron, Shell and BP spend an estimated $1.5bn (£1.1bn) on adverts in the US since the 2015 Paris agreement to tackle the climate crisis, a report shows.

London-based WPP was the leading advertising group serving the US’s oil industry over the past decade, according to analysis by the climate investigations platform DeSmog. The figure is nearly twice the respective amounts linked to its US rivals Omnicom and Interpublic Group (IPG), which merged in November.

During this period, ExxonMobil, Chevron, Shell and BP employed “deceptive and misleading” communications strategies designed to thwart policies to tackle the climate crisis by curbing the use of fossil fuels, a congressional investigation concluded in April 2024.

WPP’s services – from developing ideas for ads and designing logos, to securing ad space and analysing target audiences – were crucial to maintaining the oil industry’s public image, according to current and former WPP employees. WPP is estimated to have earned millions of dollars a year from this work.

Victoria Harvey, who has a PhD in the ad industry’s response to the climate crisis from the University of East Anglia, and reviewed DeSmog’s methodology, said: “The UK prides itself on climate leadership and yet WPP, the supposed jewel of the British advertising industry, is facilitating dangerously misleading advertising in the US. By creatively articulating the deception from big oil and gas, WPP has set the climate agenda back and continues to do so.”

ExxonMobil, Chevron, Shell and BP spent an estimated combined total of $1.5bn on buying US ad space, such as on TV and social media, since the Paris agreement, according to the analysis. That is roughly equivalent to running ads on every billboard in New York’s advertising hotspot Times Square every day for the last decade.

WPP’s global network of subsidiary advertising agencies made an estimated two-thirds’ worth of those ads, the analysis found. WPP was the only major ad company to partner with all four oil firms on advertising projects during this time.

The current and former employees said the work appeared to have breached a policy WPP adopted in 2022 not to accept projects that may “frustrate” the goals of the Paris agreement, since the oil majors were committed to increasing oil and gas production and promoting speculative climate solutions.

WPP’s agencies Ogilvy and Wavemaker have worked on US campaigns for BP and Chevron respectively, which received complaints of misleading advertising for taglines such as: “We see possibilities in planes that fly on garbage.” Neither complaint was taken forward but BP voluntarily withdrew its ads.

A 2022 US congressional committee report cited several ExxonMobil ads made by WPP’s Group SJR as examples of greenwashing, including one that compared fossil gas paired with renewable energy to “a peanut butter and jelly sandwich”.

Staff who have raised concerns have been told by seniors that they are helping clients communicate about their shift to cleaner business models, the WPP employees said. But many who have worked on these projects fear they serve primarily to deflect criticism from polluters.

BP and Shell have weakened climate targets in the past three years. At the same time, their advertising output has pivoted to promoting the necessity of fossil fuels, a report published in March by the industry campaign group Clean Creatives found.

A former employee who worked on projects for BP at the WPP branding agency Landor said: “We heard that a lot internally, that we were influencing them in the right direction. In reality, whatever BP decides to do, we would just deliver it.”

WPP and the other ad agencies mentioned did not respond to requests for comment.

Shell declined to comment. BP, ExxonMobil and Chevron did not respond to a request for comment.

Advertising companies do not publish details about how much their clients spend on ad space, and increasingly they avoid publicising their fossil fuel contracts.

To generate its estimates, DeSmog mapped the dozens of ad agencies that have worked for the four oil companies, using public sources such as staff social media profiles and industry award listings, confidential information shared by employees, and previous research by DeSmog and Clean Creatives. These contracts were then cross-referenced with ad spend estimates obtained from the market research platform MediaRadar by the University of Oxford’s Climate Litigation Lab.

Most of the oil majors’ US ad spend was channelled via subsidiaries of the handful of advertising holding companies that dominate the industry globally. After WPP, Omnicom and IPG, the Tokyo-based holding company Dentsu ranked fourth in terms of its exposure to this ad spend ($255m) and its Paris-based rival Havas ranked fifth ($230m).

The analysis did not seek to capture the millions of dollars the fossil fuel industry spends every year advertising in countries outside the US, as well as on lobbying, branding, public relations and other marketing activities.

Advertising industry insiders say momentum around climate initiatives has slowed over the past few years as competition from big technology companies and artificial intelligence has squeezed margins.

The new WPP CEO, Cindy Rose, is due to present her strategy to reverse declining profits at the company’s annual general meeting on 8 May. A preview in February did not mention sustainability.

Under the previous CEO, Mark Read, WPP committed to reduce carbon emissions and prevent greenwashing, including via the policy adopted in 2022 “not to take on any client work … designed to frustrate the objectives of the Paris agreement”. But employees claim these moves have changed little.

There are concerns that WPP’s ongoing work with Shell, BP and Chevron may breach the policy because many of these clients’ ads have distracted from or sought to justify fossil fuel expansion, according to six current and former employees, who spoke to DeSmog anonymously for fear of professional repercussions.

New fossil fuel projects planned by the companies are incompatible with the Paris goal to limit the global temperature rise to 1.5C and prevent catastrophic climate change, according to scientific assessments.

“I don’t think there’s anything that WPP could possibly be saying for BP or Shell that would adhere to the policy,” said a former director at two WPP agencies in New York.

The UN secretary general, António Guterres, has urged ad agencies to drop fossil fuel clients, calling ad executives “Mad Men fuelling the madness”.

The Organisation for Economic Co-operation and Development (OECD), an intergovernmental organisation, is considering a complaint about WPP filed by climate and human rights campaigners in February last year. At the time, a WPP spokesperson said: “Contrary to the claims being made, we adhere to the highest regulatory standards in our work for clients.”

Protesters have since targeted WPP’s Thames-front offices in London with banners reading “climate criminals”.

Additional reporting by Kathryn Clare and Ellen Ormesher