Coral used a rainbow with a leprechaun, an animated fish and a wizard to promote three online slot machine games called Rainbow Riches, Fishin’ Frenzy and Lucky Wizard.
A viewer complained that the ads were likely to be of particular appeal to children.
Coral said it had carried out an extensive review of its website to ensure it was not breaking any advertising rules.
It said the Rainbow Riches advert was “not over the top in its look, or mimicking any particular style that would make the graphics more appealing to a younger audience”.
Of the Fishin’ Frenzy ad, Coral said it had already removed a larger fish from the graphic before it was published, and that the remaining smaller fish “did not have any specific resemblance to any species that could be identified as being associated with characters from animated films that were likely to appeal to children and young persons”.
In terms of the wizard character, it said it was “the sole detail (game name aside) within the game tile”, which the firm believed “minimised the association with common fairy tale stories”.
However, the Advertising Standards Authority (ASA) found the animated leprechaun was “highly stylised” and that the ad included “a colourful background showing a bright yellow road which was an iconic fictional element in a famous children’s novel”.
The fish had large eyes and innocent-looking smiles which the ASA considered depicted them in a “cute, child-like manner”.
It said the animated wizard had a “large podgy nose, exaggerated cheekbones and a thick colourful ginger beard and a long moustache with slightly curled tips”, while the colourful background featured bright green grass, along with the name of the game being spelt in gold with stars and bolts around it.
It found that all three ads featured animated images which were likely to be of particular appeal to under-18s and were marketing gambling products, and therefore breached the advertising code.
It ruled the adverts should “not appear again in their current form”.