Apple CEO Tim Cook called for technology companies to filter out “fake news” during an interview with Good Morning Britain on Friday.

“You have to give the consumer tools to help with this,” said Cook. “We’ve got to filter out part of it before it ever gets there without losing the great openness of the internet.”

“This is one of today’s chief problems,” he continued. “It is not something that has a simple solution.”

“Fake news” has often been used as a term to describe independent or alternative news sources, particularly those with a conservative or libertarian view-point.

In November, a professor at Merrimack College, Massachusetts, included Breitbart News in her “fake news” list, which went viral online. But several news outlets have been exposed by Breitbart News for writing their own “fake news,” including the Independent, the Daily Beast, CNN (numerous times), the Atlantic, The New York Times, and The Washington Post.

There have also been several reports that Facebook is planning to team up with a range of “fact-checkers” to help filter out fake news from their platform, including the politically-biased fact-checking sites Politifact and Snopes.

Last year, it was reported that Politifact, a site which is funded by one of Hillary Clinton’s presidential campaign donors, had made 13 errors in a fact-check on Clinton Cash.

In a 2013 report, The Weekly Standard claimed that Politifact “has it out for Republicans,” after they overwhelmingly focused more on fact-checking arguments made by conservatives than Democrats, while the supposedly neutral fact-checker rated just 15% of Trump’s campaign promises as true, versus 51% for Clinton.

Politifact also fact-checked over a hundred more arguments made by Trump than Clinton.

Many of Snopes’ “neutral” fact-checkers were also discovered to be biased towards the left-wing, employing leftists almost exclusively.

Snopes fact-checker Arturo R. Garcia openly labels himself as a “progressive,” made several racially-provocative comments and attempted to compare Trump supporters to racists on Twitter, acts as the editor of “Racialicious” – “A blog about the intersection of race and culture”, and misattributed a quote about him to Breitbart News.

Fellow Snopes fact-checker Bethania Palmer attempted to link Trump to the KKK, defended a racist professor, wrote numerous left-wing articles for Raw Story, including two attempting to associate former Breitbart News executive chairman Stephen K. Bannon to domestic violence and white supremacy, and acts as a contributor for the “progressive” non-profit Truthout.

David Emery, another fact-checker and staff writer at Snopes, openly asked on Twitter whether there were “any un-angry Trump supporters.”

Despite their clear political biases, all three were tasked with fact-checking political candidates over the 2016 presidential election under the guise of a neutral service.

It was also recently revealed that David Brock’s left-wing watchdog Media Matters was “engaging with Facebook behind the scenes” to shape the social network’s handling of “fake news.”

Charlie Nash is a reporter for Breitbart Tech. You can follow him on Twitter @MrNashington or like his page at Facebook.