Using new child ‘avatar’ monitoring technology, the ASA identified 43 adverts over a two-week period in 2018 and has consequently banned five of them.
Adverts for NetEnt (Vikings Video Slot), Evoke Gaming (RedBet), Multilotto UK, Platinum Gaming (Unibet) and Skill On Net (PlayOJO) were the culprits.
The ASA’s overall findings showed gambling adverts were served to child avatars on 11 of the websites monitored, with Vikings Video Slot being responsible for 10 ads and 122 of 151 ad impressions.
The firms involved have accepted they breached guidelines, with the ASA being informed problems arose due to "errors by third-party companies."
ASA CEO Guy Parker said: "Online ads are subject to the same strict rules that apply elsewhere and this important new monitoring capability delivers on our commitment to having more impact online.
"We’re already looking at expanding this work, as well as exploring how other new technologies can help us protect the public."
Gambling Insider contacted NetEnt for comment and Henrik Fagerlund, Managing Director NetEnt Malta, has stated it has stopped all campaigns with the supplier involved.
Fagerlund said: "NetEnt takes responsible gambling and protection of minors as a matter of upmost importance and is continually striving to ensure that our games are only advertised and offered to consumers of legal age.
"We regret that this happened as a result of our collaboration with a third-party supplier and following this incident we have stopped all campaigns with this supplier. We are in close dialogue with CAP and we’re currently looking into our processes making sure we follow CAP recommendations”