Four separate gambling ads have been banned after the firms failed to ensure they were targeted away from children.
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.
LottoGo and Dunder said the ads were placed by affiliate Tapjoy, and had since terminated their relationship with them.
Betfair also said they had now stopped working with Tapjoy.
William Hill said they had blacklisted the app and would not place ads in it in future via Tapjoy or any other affiliate.
Tapjoy said the Looney Tunes app had been incorrectly categorised with a “mature-gambling” setting, which is why the ad had appeared within it.
Scopely, the publisher of Looney Tunes World of Mayhem, said they did not target their games to children, and individuals under the age of 16 in the EU are not permitted to play their games.
However the Advertising Standards Authority (ASA) said the Looney Tunes app had a rating of PEGI 7 in the UK Google Play app store, meaning it was suitable for players aged seven and up.
The game allowed players to build worlds and situations based on the Looney Tunes cartoons and collect characters to “battle” each other.
The ASA said: “Given the use of cartoon characters, cartoonish violence and the relatively simple nature of the game, we considered it was likely to appeal to many under-18s.
“However, we acknowledged that the characters would be well known to older players, and the game was likely to have more general appeal.”
It ruled that the ads must not be used again without further, specific targeting to minimise the likelihood of under-18s being exposed to them.
Betfair said: “This complaint relates to the actions of a third party publisher, which mistakenly opted in to accept adult advertising content – including from Betfair – on its app.
“This should not have happened and we immediately stopped working with the publisher once the error was discovered.”
William Hill said: “On being made aware of this issue, we immediately ceased all activities with the affiliate. We take responsible marketing extremely seriously as a business.
“We are currently conducting a full review of our ways of working with affiliates to ensure that such a situation is not repeated.”