FILE PHOTO: Senator Mark Warner (D-VA) questions David Marcus, head of Facebook's Calibra (digital wallet service), during testimony before a Senate Banking, Housing and Urban Affairs Committee hearing on "Examining Facebook's Proposed Digital Currency and Data Privacy Considerations" on Capitol Hill in Washington, U.S., July 16, 2019. REUTERS/Erin Scott/File Photo

(Reuters) - U.S. Senator Mark Warner called on Facebook Inc to provide more transparency over its decision to not fact-check ads run by politicians, asking whether it would comply with a new rule that requires online platforms to disclose the purchasers of ads.

Facebook has been under fire over its advertising policies, especially after it exempted politicians’ ads from fact-checking standards applied to other content on the social network.

Chief Executive Officer Mark Zuckerberg has earlier defended Facebook’s policy, saying that the company did not want to stifle political speech.

In a letter to Zuckerberg on Monday, Warner cited some recent ad examples which he described as containing falsehoods about former Vice President Joe Biden and said it underscored the need of accountability.

"Facebook's apparent lack of foresight or concern for the possible damages caused by this policy concerns me," Warner said in the letter. (bit.ly/2Ng3z3C)

Senators Amy Klobuchar and Warner have been pushing for the introduction of the Honest Ads Act, which would require platforms to disclose the purchasers of ads, applying the same rules that exist for TV and radio. Warner said he will press Facebook to fully comply with the act.

The social network has also drawn criticism over its ad policy from Democratic candidates, including Biden and Senator Elizabeth Warren, running in the 2020 presidential election.