Britain’s watchdog overseeing corporate marketing claims says it’s aware of a number of companies making false green statements after purchasing carbon offsets that aren’t fit for purpose.

“Some organizations are making carbon neutral and net zero claims that are entirely unqualified,” said Matt Wilson, media and public affairs manager at the Advertising Standards Authority. Such claims “are likely to breach existing rules” and the ASA is “taking proactive action immediately to crack down on such claims,” he said in statement to Bloomberg.

The comments follow an investigation published last week in the journal Science, which found that the vast majority of a potential 89 million carbon offsets issued by forest protection projects don’t represent real emissions reductions. The conclusions come as a number of major traders in the offsets market have acknowledged that they’re having to treat defunct credits as stranded assets.

“There has been a suspicion that these carbon credits lead to greenwashing,” Andreas Kontoleon, the study’s senior author and a professor of environmental economics and public policy at the University of Cambridge, said in an interview. “We now have robust and credible evidence that offset programs have deficiencies.”

The credits identified as valueless in the study have been bought by companies including Eni SpA, TotalEnergies SA, British Airways Plc and Nespresso of Nestle SA. A spokesperson for Eni, which bought more than five million of the so-called REDD+ units, said the company strongly rejects the Science study’s findings and that its carbon credits are subject to the highest standards of control.

British Airways said it’s working on a range of climate initiatives and prioritizing reducing its emissions to net zero by 2050, including by investing in sustainable aviation fuel. Nestle Nespresso said it’s moved away from investing in carbon offsets and intends to reach net zero by reducing its greenhouse gas emissions, as well as through carbon removals within its value chain. TotalEnergies didn’t respond to a request for comment.

The ASA said it will “carefully consider” the new research published in Science, including “how it feeds into our regulation in this important area,” Wilson said.

Other regulators also are voicing concerns. In the US, the Commodity Futures Trading Commission said in June that a new environmental fraud taskforce will examine green claims based on carbon credits in both derivatives and spot markets. The CFTC’s Whistleblower Office is already looking into a number of tips and complaints in this area, said Steve Adamske, director of the Office of Public Affairs at the CFTC.

In May, a class-action lawsuit was launched against Delta Airlines Inc. for its claim to carbon neutrality, which has in the past relied on purchases of carbon offsets. Delta said the lawsuit lacks legal merit.

Wilson at the UK’s ASA says cracking down on dubious carbon-neutral claims is a “key pillar” of the regulator’s climate change and environmental project as it works to ensure consumers aren’t being misled.

Earlier this year, the ASA banned a handful of newspaper, TV and poster adverts from oil companies Shell Plc, Repsol SA and Petronas International Corp., after finding them misleading. That follows a decision to ban ads by Lufthansa AG, Etihad Airways PJSC, Unilever Plc, and Hyundai Motor Co., among others, for similar reasons. The ASA says it bases it actions on assessment that steering consumer conduct can materially affect efforts to fight climate change.

--With assistance from Gautam Naik.