FTC warns Instagram influencers about not disclosing brand relationships The Federal Trade Commission sent 90 letters to celebrities and brand marketers.

 -- The Federal Trade Commission is warning social media influencers -- celebrities, athletes and other brand marketers with large online followings -- to properly disclose relationships with brands when endorsing or promoting products on Instagram.

In a Wednesday press release, the regulatory body announced that it had sent over 90 letters "reminding influencers and marketers" about the FTC's guidelines on influencer advertising in response to petitions launched by consumer rights advocacy groups like Public Citizen.

"Our goal is to influence influencers to comply with those established principles in their Instagram posts," the FTC wrote in an accompanying blog post.

In the FTC guide for commercial practices concerning the use of endorsements and testimonials, it states that the material connection between an endorser and the seller of the advertised product must be fully disclosed.

"A material connection could be a business or family relationship, monetary payment, or the gift of a free product," the FTC press release said.

But the FTC said that a number of influencer Instagram posts it reviewed left that connection ambiguous, and the disclosures were sometimes insufficient. It noted that hashtags used in some posts to denote that relationship -- including “Thanks [brand],” or “#partner” -- were not always obvious.

While not an official warning, the FTC's letters are meant to act as a reminder to influencers to stick within the proper standards for endorsing or promoting products.

Legally, it is up to both the brand and influencer to clearly disclose their marketing relationship, but the FTC said celebrities and influencers should directly make people aware of their connection and marketers should educate clients about their posts and monitor their adherence to FTC guidelines.

In its blog post, the FTC recommended three steps that influencers should take to ensure the effectiveness of disclosures on Instagram:

Keep your disclosures unambiguous.

Make your disclosures hard to miss.

Avoid #HardtoRead #BuriedDisclosures #inStringofHashtags #SkippedByReaders.