https://www.gov.uk/government/publications/social-media-endorsements-guidance-for-content-creators/social-media-endorsements-being-transparent-with-your-followers

I’m not an expert but from this link it would appear to be covered by either the asa or the cma.

More here and new law since 2025 looks to be tougher:

https://www.gov.uk/government/collections/reviews-and-social-media-endorsements-what-businesses-and-content-creators-must-know