Staff at the social network suppressed coverage of conservative politics in the US, according to a report, choosing not to include them in its trending topics section near the top of the site, despite the algorithm showing people were interested in the subject and talking about it.
"We take these reports extremely seriously, and have found no evidence that the anonymous allegations are true," said Facebook's vice president of search Tom Stocky, responding to the claims.
"Facebook is a platform for people and perspectives from across the political spectrum. There are rigorous guidelines in place for the review team to ensure consistency and neutrality. These guidelines do not permit the suppression of political perspectives. Nor do they permit the prioritisation of one viewpoint over another or one news outlet over another. These guidelines do not prohibit any news outlet from appearing in trending topics."
The element of human curation in trending topics was brought to light by the same publication, raising concerns over Facebook's influence.
Curators were told to add topics which weren't popular or trending into the section, and that some stories which which were popular were suppressed, an unnamed source claims. This includes stories about Mitt Romney, Glenn Beck and Rand Paul.
It's also claimed that stories from publications such as the BBC, CNN and the New York Times, were chosen over the same stories from more conservative leaning sites such as Drudge Report and Brietbart.
"Trending topics is designed to showcase the current conversation happening on Facebook. Popular topics are first surfaced by an algorithm, then audited by review team members to confirm that the topics are in fact trending news in the real world and not, for example, similar-sounding topics or misnomers," Stocky continued.
Mark Zuckerberg has spoken out against Republican presidential wannabe Donald Trump in the past. However, Facebook will remain a sponsor the Republican National Convention where Trump is expected to officially become the party's chosen candidate.