SAN FRANCISCO, May 23 (Reuters) - Facebook Inc will no longer rely on a top-10 list of websites to help choose items for its Trending Topics section, even though an internal probe showed no evidence of political bias in the selection process, the company said on Monday.
The world's largest social media network said in a blogpost that changes include clearer guidelines for human editors on the Trending Topics team, more training to emphasize avoiding ideological or political basis, and more robust review procedures.
The internal investigation was prompted by a letter from Republican Sen. John Thune earlier this month demanding that the company explain how it selects news articles for its "trending" list.
A former Facebook contractor had accused the company's editors of deliberately suppressing conservative news. The allegations were reported by technology news website Gizmodo, which did not identify the ex-contractor.
Facebook said its investigation showed that conservative and liberal topics were approved as trending topics at nearly identical rates. It said it was unable to substantiate any allegations of politically motivated suppression of particular subjects or sources.
In his letter, Thune called on Facebook to respond to criticism that it suppressed conservative news and sought answers by May 24 to several questions about its internal practices.
"Any attempt by a neutral and inclusive social media platform to censor or manipulate political discussion is an abuse of trust and inconsistent with the values of an open Internet," Thune said.
Facebook Chief Executive Mark Zuckerberg last week met with more than a dozen conservative politicians and media personalities to discuss issues of trust in the social network.
(Reporting by Yasmeen Abutaleb in San Francisco and Sangameswaran S in Bengaluru; Editing by Mary Milliken and Richard Chang)