Facebook chief executive Mark Zuckerberg has said the company is investigating claims it censored news reports with conservative viewpoints.
It follows a week of allegations in the media and discussion in the US Senate.
The tech news website Gizmodo had said Facebook staff suppressed articles on conservative topics from the site’s “trending” news section and “injected” others, even if they were not trending.
Mr Zuckerberg said Facebook had found no evidence the report was correct.
“Facebook stands for giving everyone a voice,” he wrote in a post.
“This week, there was a report suggesting that Facebook contractors working on Trending Topics suppressed stories with conservative viewpoints. We take this report very seriously and are conducting a full investigation to ensure our teams upheld the integrity of this product.”
He said if any evidence of “anything against our principles” was discovered “you have my commitment that we will take additional steps to address it”.
Mr Zuckerberg said he was inviting leading conservatives to meet him to discuss their views.