Social media influencers are increasingly paid, or otherwise rewarded, to promote and endorse goods and services but may not be fully disclosing this.

Consumer protection law means where influencers are paid or rewarded to promote, review or talk about a product in their social media feeds, it must be made clear.

As part of its investigation, the CMA has written to a range of celebrities and social media influencers to gather more information about their posts and the nature of the business agreements they have with brands.

The CMA investigation is considering the extent to which influencers are clearly and accurately identifying any commercial relationships, and whether people are being misled.

George Lusty, the CMA’s senior director for consumer protection, said: “Social media stars can have a big influence on what their followers do and buy. If people see clothes, cosmetics, a car, or a holiday being plugged by someone they admire, they might be swayed into buying it.

“So, it’s really important they are clearly told whether a celebrity is promoting a product because they have bought it themselves, or because they have been paid or thanked in some way by the brand.”

If the CMA finds practices that break consumer protection law, it can take enforcement action.

The CMA is asking the public to share their experiences.

The CMA is working closely with the Advertising Standards Authority (ASA) in this area. In March the ASA issued a call for evidence to find out more about what labels help people understand when the online content they see, hear and interact with is advertising.

Yuval Ben-Itzhak, CEO of social media marketing agency, Socialbakers, said of the CMA investigation: "Influencer marketing on Instagram is now one of the fastest growing marketing trends and as such is under the spotlight. If brands want to build and retain customer trust, they need to be transparent with their audiences about the posts they are paying for and the influencers they are working with."