When InsideClimate News won a Pulitzer Prize in 2013 for national reporting, one of its writers told the New York Times she hoped that people who considered her publication advocacy journalism would take note of the award and “stop making that mistake.”

InsideClimate News may be the most influential — and controversial — environmental publication you’ve never heard of. Despite its tiny staff, shoestring budget, and low name recognition, the nonprofit has won several prestigious awards for its content and forged major partnerships with, among others, the Associated Press, the Weather Channel, the Guardian, and Bloomberg.

Its supporters say InsideClimate News is a pioneer of nonprofit advocacy journalism, successfully competing with traditional media and churning out high-impact investigative stories on under-reported environmental news. “In this community, they’re seen as an example of how you can be successful and develop the skills and the reputation and do deep dives on stories asking good questions,” says Beth Parke, executive director of the Society of Environmental Journalists. InsideClimate News has won two reporting awards from the organization in the past year.

But its critics claim that InsideClimate News is essentially a mouthpiece run by a public-relations consultancy that gets its funding almost exclusively from groups with an environmental agenda. A National Review examination of tax filings, corporate and trademark paperwork, and other public records involving the nonprofit and its partners has raised even more questions about InsideClimate News, its origins, and its funding.

InsideClimate News was founded by David Sassoon, a man with deep roots in public relations. He makes no secret of his views on climate change, writing for DeSmogBlog about his desire “to make history by working hard and doing what I can to usher in the clean energy economy.”

Before Sassoon built InsideClimate News, he worked as a senior vice president at PR consultancy Rowland Communications Worldwide, where he helped promote the interests of bio-tech companies. In 1999, Rowland Communications filed a trademark for Science First Communications, listing its services as advertising, promotion, media planning, and marketing. And in a March 2001 interview with PR Week, Sassoon elaborated about what Science First did:

Two years ago, we had several clients who were emerging and not yet to market. . . . We decided that we needed to help them sell their science. We called it “Science First.” We trademarked it. It really gave them leverage in the investor community. Now, those biotechs are at the stage where they have to take their product to market, and then it becomes like launching a pharmaceutical.

Just a month later, Rowland Communications abandoned its trademark, but Sassoon continued to do public-relations work through Science First. Between 2004 and 2005, at least five news releases about biotechnology and health care list Sassoon as the media contact, mentioning Science First.

In April 2004, Sassoon registered with the state of New York an entity called Lost Light Projects Inc., which today does business as InsideClimate News. And in August 2006, he also registered Science First as a New York corporation, listing himself as the chief executive officer. And as late as 2012, the activist environmental law firm EarthJustice named both Sassoon and Science First on its list of clients and partners.

Links between the two entities abound. The nonprofit news organization InsideClimate News and the PR consultancy Science First are frequently mentioned together in public records, listed as though they are interchangeable. And by at least one credible account, Science First serves as the official publisher of InsideClimate News.

It isn’t necessarily unethical for a public-relations consultancy to publish a nonprofit news publication, says Fred Brown, an ethics expert for the Society of Professional Journalists. “But it ought to be ethical PR work, and ethical PR includes transparency,” Brown says. He adds: “Any time an entity is not transparent about its origins, it raises suspicions, and rightly so. . . . If you want to be credible, you’ve got to be transparent. And that includes being clear about who is supporting you financially, philosophically, whatever, politically.”

Sassoon declined National Review’s repeated requests for an interview, also failing to answer detailed questions e-mailed to him about Science First and InsideClimate News. “Our donors support our independent, award-winning journalism and do not have access to our editorial process or decision-making,” he replied in an e-mail, refusing to comment further.

Michael Thatcher, president and CEO of the nonprofit watchdog Charity Navigator, called the lack of transparency about InsideClimate News “at face value, troubling.” “The fact that they’re [apparently] owned by a PR agency isn’t in and of itself illegal, but there’s some huge potential conflicts of interest. . . . 

The fact that people are unwilling to speak to you and you’re getting that kind of evasiveness — that’s a bit of an alarm,” Thatcher says.

InsideClimate News lists some of its donors on its website — and many of these organizations belong to what in a minority report of the Senate Committee on Environmental and Public Works is described as “an elite group of left-wing millionaires and billionaires, [known as] the ‘Billionaire’s Club,’ [which] directs and controls the far-left environmental movement, which in turn controls major policy decisions and lobbies on behalf of the U.S. Environmental Protection Agency.”

Tax filings show that environment-minded foundations and nonprofits seemed to consider Science First and InsideClimate News synonymous, often giving them money through another nonprofit, NEO Philanthropy, which served as the “fiscal sponsor” for both of the entities from 2010 to 2014, a representative for the nonprofit says.

NEO Philanthropy, also known as Public Interest Projects, would not answer National Review’s questions about its involvement with Science First or InsideClimate News. But on its recent tax filings, NEO Philanthropy lists Science First as one of its largest contractors, paying Sassoon’s company nearly $2.6 million between 2008 and 2014 for “project management.”

In 2012 and 2013, the Marisla Foundation, which runs an environmental grant program, gave $450,000 in total to Public Interest Projects, in support of Science First and InsideClimate News. In 2011, Marisla gave two grants of $150,000 each to Public Interest Projects for “Science First/Federal Climate Policy Communications Initiative.”

The Marisla Foundation would not give National Review an interview or answer questions about whether the Federal Climate Policy Communications Initiative was a public-relations or lobbying push. “They stand firmly behind their initial request to not comment at this time or any other time in the future,” their spokesperson at Foundation Source said by e-mail, adding that she also did not want to be contacted again by National Review.

Likewise, the Park Foundation, also listed as a member of the “Billionaire’s Club,” gave $25,000 to Public Interest Projects. According to the foundation’s website, the grant money paid for InsideClimate News to report on the petcoke industry and on air and water pollution caused by fracking.

The Park Foundation did not respond by deadline to National Review’s repeated queries. Sassoon did not respond to questions about whether InsideClimate News could accept such subject-targeted grants while maintaining editorial independence.

The energy industry has criticized the lack of transparency around InsideClimate News, noting that many of their biggest funders also support environmental organizations such as the Sierra Club and Earthworks and environmental activists including 350.org founder Bill McKibben.

“There’s this really weird kind of shell or background to who they are,” says Steve Everley, a spokesperson for Energy in Depth, an organization founded by the Independent Petroleum Association of America. A longtime critic of InsideClimate News, Everley says he sees as simple hypocrisy this widespread failure to answer questions about the publication.

“Ironically, these are the same entities and organizations that want to focus like a laser on every single report if it’s coming from the [energy] industry,” he says. “So it’s interesting — they call for disclosure, they want the industry, everything they do, to be out in the open and public, and most of the time, it is — and yet they refuse to acknowledge that there’s any sort of influence over funding unless it’s on a particular side of an issue.”

The little that is known about InsideClimate News raises questions about conflicts of interest as well as about the publication’s ability, and proclivity, to report fairly and without bias. One might wonder why none of the publication’s many major media partners aren’t raising similar concerns.