Advertising Standards Authority
From RationalWiki
The Advertising Standards Authority is the UK advertising industry's self-regulatory body, dealing with misleading advertising in the UK so as to head off more stringent government regulation. Surprisingly, it actually works really well.
An ASA ruling has no direct legal force. However, being ruled against and then defying the ruling makes a conviction under trading standards regulations almost a slam-dunk.
It is a particular delight when dealing with the claims of alternative medicine woomeisters, and getting them to stop claiming dangerous rubbish.