US media on Tuesday evening was abuzz with reports that John Thune, a Republican senator from South Dakota, had sent a letter to Facebook demanding to know how it curates its "Trending Topics" news breakdown.

Thune is the chairman of the Senate Commerce, Science and Transportation Committee, which gives him oversight on media and internet issues.

The letter, published in full on the tech site "Gizmodo," asks CEO Mark Zuckerberg to personally respond to allegations that "'news curators' responsible for managing Facebook's 'Trending Topics' section frequently targeted stories on conservative political topics for exclusion."

"If Facebook presents its Trending Topics section as a result of a neutral, objective algorithm, but it is in fact subjective and filtered to support or suppress particular political viewpoints, Facebook's assertion that it maintains 'a platform for people and perspectives from across the political spectrum' misleads the
public," wrote Thune.

Thune goes on to demand Zuckerberg provide an organization chart for the employee makeup of the feature, and asks if Facebook is doing anything to investigate his claims.

'Designed to surface popular conversations'

Facebook responded within a few hours, saying that "'Trending Topics' is designed to surface popular conversations - no matter where they fall on the political spectrum." The statement added that they "look forward to addressing" Thune's questions.

News outlets like "Mother Jones" magazine have reported anonymous quotes from inside the social media giant alleging that news curators would bump conservative-themed stories from the lineup if they didn't like the person or topic that was trending.

Reactions on social media slammed Thune, arguing that even if the charges were true, a private company has the right to publish whatever news stories it wishes to.