Instagram influencers, both big and small, are the subject of the prying eyes of consumer protection bodies in the US and UK amid the crackdown over lump sums from endorsements. While it remains a no-mystery that social media is today's most cost-effective form of advertisement, authorities are now running after big brands and influencers discreetly using the platform.

There has been an ongoing debate in the advertising industry whether consumer protection bodies should take over the digital media space. As fine line settles between what is recommended and what is marketed, advertising authorities have found a reason to take action against influencers for endorsing brands in exchange for payment.

Also read: Instagram in trouble for deleting mother son's picture

Earlier this week, the UK Advertising Standards Authority (ASA) ordered reality TV personality Sophie Kasaei to take down her photo of the Flat Tummy Tea in March. Although it was marked as an advertisement in accordance with the organisation's regulation, the decision was rolled out because Kasaei's claims that it could decrease water weight is in violation of rules marketing enclosing health and nutrition claims.

Last week, the US Federal Trade Commission (FTC) sent letters to 21 celebrities to remind them of their obligations to clearly disclose whether or not their posts are sponsored. Some of them include Naomi Campbell, Lindsay Lohan, Sofia Vergara, Amber Rose and Vanessa Hudgens. They are given until 30 September to respond.

"This should send a message that such connections must be clearly disclosed so consumers can make informed purchasing decisions," says Maureen Ohlhausen, the acting FTC chairperson.

In the meantime, Instagram recently announced to introduce its first-ever branded content policy to help influencers clearly draw the line and regulators to track them down.