The Advertising Standards Authority has banned an advertisement for EA's app game Dungeon Keeper after declaring it 'misleading'.
The UK independent regulator found that the email ad did not make it clear that the game charges players for certain in-app purchases, which 'have a significant impact on gameplay'.
Although the game is technically free to play, gamers can pay to speed up their progress (by mining gems and areas faster) - and the ASA says the EA ad didn't make this clear.
It's a warning shot to gaming vendors/publishers who work with 'free-to-play' games - titles that are free to play but charge money for in-game extras. These types of games are becoming increasingly popular on PC, with millions of players using games such as League of Legends and Dota 2 every month.
The original complaint over the Dungeon Keeper ad was made by games journalist Chris O'Regan, who said: "In February of this year I received an email from EA suggesting I download Dungeon Keeper on iOS and Android 'for free'. Knowing how that particular game forces the player to continually pay small fees in order for it to function as originally intended, the ad was decidedly misleading.
"Noting this I wrote to the Advertising Standards Association and alerted them to this transgression on the part of EA. They then set about carrying out an investigation to determine whether my complaint had merit. After five months of research they decided it did.
"They have now levied a formal complaint against EA and by doing so defined the concept of 'free-to-play'.
The ASA added: "We noted that the ad did not include any reference to in-app purchases or the role they would play. Although we acknowledged that a disclaimer about the inclusion of in-app purchases was placed on the product page on the stores in which the app appeared, we noted that this was not within the body of, or linked to, the original ad, and that it did not make the nature of these purchases clear.
"Because the game had the potential to restrict gameplay beyond that which would be expected by consumers and the ad did not make this aspect of the role of in-app purchasing clear, we concluded that it was misleading."
EA said that in their view they had not misled or omitted information from the ad.