The five issues it identified as most important were: brand safety, viewability, ad fraud, ad blocking and privacy.

For brand safety, 36 companies trading digital display ads are now certified against DTSG Good Practice Guidelines; it has launched the second certification of viewability vendors to reduce discrepancies and has developed a certification programme and created Good Practice Principles for ad fraud.

IAB UK has launched DEAL, a set of options to help publishers with ad blocking and when tackling privacy, it has set up a working group to respond to the EU GDPR (General Data Protection Regulation).

Guy Phillipson, IAB UK’s CEO, said: "Despite growing at its fastest rate for seven years, digital advertising continues to face a number of medium term challenges. We’ve made good progress but, of course, there’s still plenty of work to be done, by everyone involved in the industry."