Microsoft and other US tech companies successfully lobbied the EU to hide the environmental toll of their datacentres, an investigation has found, with demands to block a database of green metrics from public view written almost word for word into EU rules.

The secrecy provision, which the European Commission added to its proposal almost verbatim after industry lobbying in 2024, hinders scrutiny of the pollution that individual datacentres emit. It leaves researchers with just national-level summaries of their energy footprints.

The rise of AI chatbots has spurred a boom in the construction of chip-filled warehouses with a hunger for power that is being met, in part, by burning fossil gas. Legal scholars warn the blanket confidentiality clause may fall foul of EU transparency rules and the Aarhus convention on public access to environmental information.

“In two decades, I cannot recall a comparable case,” said Prof Jerzy Jendrośka, who spent 19 years on the body overseeing the convention and teaches environmental law at the University of Opole in Poland. “This clearly seems not to be in line with the convention.”

Documents obtained by Investigate Europe, an independent journalism cooperative that led the research in collaboration with the Guardian and other media partners, show the rules have already been used to shield datacentres from scrutiny.

In an email citing the secrecy clause last year, a senior commission official reminded national authorities of their obligation to “keep confidential all information and key performance indicators for individual datacentres”.

“It is really important to reiterate this point as the commission has already received various requests for access to documents by the media or the public in relation to the data,” the official said. “All these requests have been so far refused.”

The US and China have led the global AI boom but even in Europe datacentres are being built at breakneck speed. The EU aims to triple its datacentre capacity in the next five to seven years as it seeks to position itself as a global leader in artificial intelligence.

In a move to increase transparency, the commission updated its energy efficiency directive in 2023 to oblige datacentre operators to report data on key performance indicators. In further guidance, it proposed publishing “aggregated” environmental metrics.

But during public consultations in January 2024, tech companies pushed to classify all individual information on datacentres as confidential, citing commercial interests. The demand means the data cannot even be accessed through freedom of information requests.

The final text of the article, which differs by just a couple of words from industry demands, states “the commission and member states concerned shall keep confidential all information and key performance indicators for individual datacentres that are communicated to the database … Such information shall be considered confidential information affecting the commercial interests of operators and owners of datacentres.”

Industry submissions during the public consultation show the groups who lobbied for the change are Microsoft; DigitalEurope, an industry organisation whose members include Microsoft, Google, Amazon and Meta; and Video Games Europe, whose members include Microsoft and Netflix.

Ben Youriev, a researcher at InfluenceMap, a not-for-profit organisation that tracks corporate lobbying, said it was an example of how the tech sector was reckoning with a shift towards using more energy.

He said: “Where the industry was previously outspoken in its support for clean energy and emissions reductions, many firms have since fallen silent. Instead, they appear to be prioritising the rapid build-out of datacentre infrastructure globally over supporting clean energy and rapid emissions reductions.”

DigitalEurope did not respond to a request for comment. The commission and Video Games Europe declined to comment.

Microsoft said it supports greater transparency around datacenters as sustainability disclosures can help drive better outcomes and build public trust. A spokesperson said: “We are taking further steps to increase openness, while protecting confidential business information.”

The EU executive considers the regulation a first step to creating a common EU rating scheme for datacentres. In a second phase, for which public consultation on the legislation ends this month, it plans to publish sustainability scores from the database to “make it easier to compare different datacentres in a same region and promote new designs or appropriate efficiency in datacentres”. Under the current proposals the majority of what operators report would remain confidential.

The commission’s internal position, according to sources close to the matter, is that making each datacentre’s information public might lead operators to stop reporting their sustainability metrics. However, EU data shows that only 36% of eligible datacentres have complied with the existing reporting requirements.

The industry has “a real interest in keeping the numbers hidden”, said Alex de Vries-Gao, a researcher at Vrije Universiteit Amsterdam, who has mostly had to rely on aggregated data when seeking to quantify the environmental footprint of AI.

“Public information is extremely limited. You typically have to bend over backward to come up with any numbers,” he said.

The EU is obliged under the Aarhus convention to ensure that environmental information is systematically made available by the authorities to the public.

Luc Lavrysen, the former president of the Belgian constitutional court and emeritus professor of environmental law at Ghent University, said the confidentiality clause “is clearly in violation” of EU transparency rules and the Aarhus convention.

Kristina Irion, an associate professor in information law at the University of Amsterdam, reached the same conclusion. She said the “sweeping presumption of confidentiality” incorrectly benefits corporate interests over public access to at least some of the data.

“What deserves protection as confidential information affecting the commercial interests of datacentre companies should be determined on a case-by-case basis,” she said.