Adverts for some of the biggest gambling companies appeared in a mobile gaming app which appealed to children, the ASA advertising watchdog has ruled.

Ads for LottoGo EuroMillions, William Hill Vegas, Betfair Bingo and Dunder appeared within the Looney Tunes World of Mayhem app in February.

The app gave players the opportunity to earn “gems” to use in the game by viewing ads or performing tasks.

The ASA ruled that the ads must not be used again without specific targeting to minimise the likelihood of under-18s being exposed to them. LottoGo and Dunder said the ads were placed by an affiliate company called Tapjoy, and it has since terminated the relationship. Betfair also said it had stopped working with Tapjoy.

William Hill added that it had blacklisted the app. Tapjoy insisted the Looney Tunes app had been incorrectly categorised with a ‘mature gambling’ setting meaning it was only designed for adults, which is why the ads appeared within it. Scopely, the publisher of Looney Tunes World of Mayhem, said it did not target games at children.