Critics are blasting a draft U.N. climate change report that combines studies by advocacy groups like the World Wildlife Fund and Greenpeace alongside scientific research papers -- the same issue that led independent auditors to slam the U.N.'s last report.

“You'd think that the IPCC would have learned its lesson, that it would have told its authors not to rely on these sorts of publications,” said Donna Laframboise, the head of nofrakkingconsensus.com, an investigative website skeptical of the scientific consensus on global warming.

“The report currently includes, amongst its list of references, nine separate publications produced wholly or in part by the WWF,” Laframboise told FoxNews.com.

'The report currently includes nine separate publications produced wholly or in part by the WWF.'

— Donna Laframboise, head of nofrakkingconsensus.com

This isn’t the first time the WWF has been used as a source in a climate assessment report by the U.N.'s IPCC, the Intergovernmental Panel on Climate Change. In 2007, the panel relied on statements made in a WWF article to predict that the Himalayan glaciers would melt by 2035. That claim was based on nothing more than a remark that a scientist made in a 1999 interview with New Scientist magazine.

A 2010 audit by a panel of scientists from around the world called for change, meaning less so-called "gray literature," and the IPCC apologized for the error.

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“The WWF has a definite opinion about whether humans are responsible for global warming. It wants more people to think the way it does,” Laframboise said. Some scientists say such reports should generally not be cited.

“In general, I don’t think reports by advocacy groups are credible,” John Christy, a climatologist at the University of Alabama in Huntsville, said.

But others argue that groups like the WWF do important research.

“If it's legit research, it's fine,” said Aaron Huertas of the Union of Concerned Scientists. “Sometimes they're the only ones with relevant data for a certain topic, such as energy production.”

Laframboise says that WWF’s mission itself calls into question whether it can do objective science.

“On its website, the WWF invites people to join its ‘environmental campaigning community’ … It's therefore accurate to describe the WWF as an activist group,” she said.

Another bone of contention regards who may review the U.N. climate reports in advance. Laframboise helped a leaker publicize two USB data sticks full of information on the U.N. climate report on her site.

“These [documents] reveal that two WWF employees, as well as employees from other activist groups, were designated as 'scientific expert reviewers' by the IPCC,” Laframboise said.

Then, she says, the “experts” used their influence to plug their group’s work.

“What we see here is the WWF... using the IPCC's expert review process as a behind-the-scenes lobbying opportunity. Again and again, these WWF employees urge IPCC authors to base their analysis on WWF publications,” she said.

She found that one WWF employee, Sarah Evans, asked the IPCC four times to cite a particular WWF handbook.

But IPCC officials say that the review process is open to anyone.

“We do not select the reviewers -- experts register to take part in the review based on a self-declaration of expertise,” said Jonathan Lynn, head of communications and media relations at the IPCC.

“The IPCC encourages reviews from as broad a range of experts as possible, including experts from business, NGOs and the scientific community,” Lynn told FoxNews.com. “The aim is for IPCC reports to represent the latest scientific, technical and socio-economic findings and be as comprehensive as possible.”

The review process for the leaked draft has not been completed, but “expert reviewers on the [previous] Fourth Assessment Report (AR4) that came out in 2007 included people from the American Petroleum Institute, BASF, Boeing, Chevron, DuPont, ExxonMobil, GE and Siemens,” Lynn said.

Still, critics believe that including any advocacy groups in the review process is a problem.

“The real issue is that all of the evidence is being evaluated either by people who embrace an activist worldview, or who don't consider an activist worldview to be at odds with rigorous science,” Laframboise said.

“The IPCC sees nothing wrong with activist perspectives. That's what gives the game away. That's what tells us that what's going on at the IPCC is not science.”