Facebook (NASDAQ: FB) is defending itself over claims its Trending Topics intentionally suppressed stories supporting conservative political viewpoints.
A report by technology news site Gizmodo said staff responsible for what was shown to Facebook's 1.6 billion users frequently chose to bury articles they did not agree with.
Responding to the allegations, the network's head of search Tom Stocky wrote that the site "found no evidence that the anonymous allegations are true".
The claims come weeks after Facebook founder Mark Zuckerberg publicly denounced the policies of likely U.S. presidential nominee Donald Trump.
However, Facebook insisted Zuckerberg's view did not influence what stories are given added visibility on the network.
Human curation
The Trending Topics column appears in the top right corner of a typical Facebook page. It is designed to highlight what subjects are being discussed heavily by Facebook users around the world.
The Gizmodo story, which quoted a person it said they had been one of the editors, alleged Facebook staff were routinely tampering with Trending Topic stories.
Gizmodo's source added that staff were told to seek out stories published on mainstream sites ahead of publications with a clearly stated political bias - even if the stories originated on those smaller outlets.
Also, if several mainstream media sites were covering the same story, Facebook would - according to the source - artificially place it in the Trending Topic column, even if it was not being discussed heavily by users.
Breitbart, one of the leading conservative news sources in the U.S., said the reports confirmed what they had "long suspected", that "Facebook's trending news artificially mutes conservatives and amplifies progressives".
The anonymous source also claimed that stories staff favoured - such as the Black Lives Matter movement - were given artificially greater prominence. Facebook said that this was "untrue".
Facebook shares opened Tuesday up 51 cents, or 0.4%, from Monday's close, at $119.75 U.S., within a 52-week trading range of $72.00 to $120.79 U.S.
