Updated: Will Heartland Institute scandal force transparency on corporate donors?

Companies have been warned they must be more transparent about their funding of lobbying groups in the light of leaked documents that apparently detail corporate donations to US climate-sceptic think-tank the Heartland Institute.

The documents, at least one of which Heartland has insisted is a fake, reveal the controversial group hopes to raise almost $4.5m in corporate donations during 2012, alongside $1.25m from a long-standing anonymous donor.

Microsoft, Diageo and GlaxoSmithKline are among those donors or targeted donors that have promoted a strong environmental image that seems at odds with the think-tank's stated aim of showing "the topic of climate change is controversial and uncertain".

The documents suggest Microsoft paid $59,908 to Heartland in 2011, GlaxoSmithKline (GSK) paid $20,000 in 2011 and $30,000 the year before, Pfizer provided $130,000 in 2010, and Diageo gave $10,000 in 2010 and is expected to shell out another $10,000 in 2012.

A spokeswoman for GSK sought to distance the company from the Heartland Institute's work on climate change. "GSK absolutely does not endorse or support the Heartland Institute's views on the environment and climate change," she said. "We have in the past provided a small amount of funding to support the Institute's healthcare newsletter and a meeting."

A spokeswoman for Diageo took the same line, adding that future contributions would be scrutinised.

"Diageo provided a small contribution (nearly two years ago) to Heartland Institute - related to an excise tax issue," she said. "We vigorously oppose climate scepticism and our actions are proof of this. We will be reviewing any further association with this organisation."

Microsoft said that its donation comprised free software licences on Heartland's request as part of its global nonprofit software donation programme.

"Microsoft believes climate change is a serious issue that demands immediate, worldwide attention and we are acting accordingly," a spokeswoman said. "We are pursuing strategies and taking actions that are consistent with a strong commitment to reducing our own impact as well as the impact of our products."

Pfizer had not responded to requests for comment at the time of going to press.

The contested documents also reveal how Heartland is working on plans for a new school curriculum with the goal of "dissuading teachers from teaching science", and sponsors the Nongovernmental International Panel on Climate Change (NIPCC), a network of climate sceptic scientists that attempts to debunk UN reports.

While companies are more than entitled to spend promotional budgets however they like, they should be open about where money is flowing so they can be held accountable by shareholders and other investors, Bob Ward, policy director at Grantham Research Institute on Climate Change and the Environment at LSE, told BusinessGreen.

"The big questions is: in the age of corporate social responsibility why are they not being upfront about the groups they are funding and their reasons for doing it," he said. "It's a double standard – these companies demand transparency from climate change researchers [but] don't reveal their own funding.

"For [companies] founded on science and engineering, it's difficult to see how they could support an organisation that is so ideological rather than scientific," he added. "The question for any company is: is that really the type of group you want to be associated with?"

John Grant, author of the Green Marketing Manifesto, described the affair as "a monumental fuck up" in terms of managing corporate brand risk and credibility.

He warned that companies linked to the Heartland Institute could irrevocably damage relationships and undo the benefits of years of positive work unless they explained their motives.

"What a travesty for companies that have a strong stance on sustainability," he told BusinessGreen. "We're in the era of Wikileaks and companies should take the view that people outside can discover anything, so they need to be transparent. The worst thing you can do is put your head down."

But he added that being uncovered in this way could force companies to move quicker on the issue than they might have under legal requirements – a point also made by Ed Gillespie, co-founder of sustainability communications agency Futerra.

"I think it could be a brilliant thing," Gillespie told BusinessGreen. "Companies have been going around saying one thing publicly and doing another thing privately, and you can't get away with it anymore.

"It flushes [corporate behaviour] out into the open and will force companies to define if they are climate sceptics or not."

Gillespie did concede that the size of the corporations involved could mean breakdowns in communication between corporate affairs and sustainability teams. He also acknowledged that Heartland campaigns against a range of regulations, not just environmental rules.

"There's also an issue of proportionality," he added. "The amount given could be miniscule compared with the overall corporate affairs budget. They could have only sponsored an event or lunch."

However, for Andrew Pendleton, head of campaigns at Friends of the Earth, the value of a donation is not the issue.

"These are not big amounts of money, but that's not the point," he told BusinessGreen. "Some of these companies would purport to be going green... but if they're not willing to be open, we have to ask why.

"The Heartland Institute is at the centre of poisoning the debate in the US, but that debate has to be carried over here. It raises the question of whether [these companies] may turn out to be funding UK groups as well."

This article was updated to reflect the Heartland Institute's statement.