(Reuters) - Facebook Inc FB.O said on Friday it was allowing U.S.-based political candidates to run branded content on its social networking platforms, but the content would not be cataloged in its advertising library.

Political campaigns and groups can now use the social media company’s branded content tool, which allows influencers to more clearly tag in an official sub-header that the post is a paid partnership.

The change came after U.S. Democratic presidential candidate Michael Bloomberg this week paid popular meme accounts on Facebook-owned Instagram to post content about the billionaire former New York mayor.

The strategy of paying social media influencers to spread political messages or make content is gathering momentum ahead of the 2020 race, but rules around the practice have been hazy.

“After hearing from multiple campaigns, we agree that there’s a place for branded content in political discussion on our platforms,” a Facebook spokesman said in a statement.

The Instagram posts by popular meme accounts that were paid for by the Bloomberg campaign did include disclaimers, but their humorous nature left some users wondering if the partnerships were real. Several posts used the disclaimer: “And yes this is really #sponsored by @mikebloomberg.”

To use Facebook’s branded content tool, political campaigns or groups must be authorized as political advertisers through the company’s ID verification process.

FILE PHOTO: Facebook logos are seen on a screen in this picture illustration taken December 2, 2019. REUTERS/Johanna Geron/Illustration/File Photo

Facebook does not make money from branded or sponsored content, for which brands directly pay creators, so they do not count this as advertising. It does, however, ask content creators to comply with regulations to disclose paid partnerships.

The Federal Trade Commission requires social media influencers and content creators to clearly label sponsored posts. This week, the FTC announced it would be seeking public comment on how effective these rules are and whether it should make changes.

The Federal Election Commission says paid public online communications containing “express advocacy” must have a disclaimer, but it does not have explicit rules about social media influencers.

In December 2019, former FEC chair Ellen Weintraub acknowledged in a statement that its 2006 internet disclaimer regulations were written “several eons ago.”

Facebook said sponsored content from political advertisers will not be included in its Ad Library, a database maintained to provide transparency around political and other advertising, unless the creator pays to promote the post using the company’s advertising tools.

Bloomberg’s Democratic rival Senator Elizabeth Warren criticized the fact that sponsored posts would not be publicly tracked.

“Refusing to catalog paid political ads because the Bloomberg campaign found a workaround means there will be less transparency for the content he is paying to promote,” Warren said in a tweet. “Mike Bloomberg cannot be allowed to buy an election with zero accountability.”

The Bloomberg campaign, which has been waging a huge digital campaign to try and beat Republican President Donald Trump in November, told Reuters this week that it thought its “meme strategy” would be effective.

“The campaign was explicitly clear that these posts were ads and sponsored content,” said Sabrina Singh, a spokeswoman for the Bloomberg campaign, in a statement on Friday. “We went above and beyond to follow Instagram’s rules and the text of the post clearly shows these are the campaign’s paid ads.”

A Facebook spokesman told Reuters that the Bloomberg campaign was not the only political campaign that had asked about the company’s policies regarding sponsored content.