A journalism watchdog has been forced to scrap a list of “unreliable” news sources because, as it turns out, the list wasn’t reliable.

The Poynter Institute, a journalism nonprofit organization, initially released a list of more than 500 “unreliable” news outlets purportedly “built from pre-existing databases compiled by journalists, fact-checkers and researchers around the country.”

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But a number of prominent conservative-leaning outlets were included in the “unreliable” category, including The Washington Examiner, Washington Free Beacon, Daily Caller and other publications that employ scores of journalists covering Congress, elections, the White House and more. The index was created with the help of an employee for the Southern Poverty Law Center.

The walk-back was gradual. First, the authors reversed the inclusion of The Washington Examiner after further review. But the paper's executive editor, Philip Klein, complained that the group was still urging an advertiser blacklist for those outlets still included -- calling the process behind the list opaque and arbitrary.

Poynter’s managing editor, Barbara Allen, posted a mea culpa Thursday as the backlash built.

“On Tuesday, April 30, Poynter posted a list of 515 'unreliable' news websites, built from pre-existing databases compiled by journalists, fact-checkers and researchers around the country. Our aim was to provide a useful tool for readers to gauge the legitimacy of the information they were consuming,” the statement read.

“Soon after we published, we received complaints from those on the list and readers who objected to the inclusion of certain sites, and the exclusion of others. We began an audit to test the accuracy and veracity of the list, and while we feel that many of the sites did have a track record of publishing unreliable information, our review found weaknesses in the methodology.

“We detected inconsistencies between the findings of the original databases that were the sources for the list and our own rendering of the final report.”

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It continued: “Therefore, we are removing this unreliable sites list until we are able to provide our audience a more consistent and rigorous set of criteria. The list was intended to be a starting place for readers and journalists to learn more about the veracity of websites that purported to offer news; it was not intended to be definitive or all encompassing.

“We regret that we failed to ensure that the data was rigorous before publication, and apologize for the confusion and agitation caused by its publication. We pledge to continue to hold ourselves to the highest standards.”

The institute continued to face fallout for the blunder, with many noting the irony of how the "unreliable" news outlets list was itself not reliable.

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The databases curated to create the list included ones maintained by Annenberg Public Policy Center, Snopes, PolitiFact, and Merrimack University, researcher Barrett Golding wrote in a now-deleted report explaining the botched index.

Golding is also a producer with the Southern Poverty Law Center.