The South Korean Game Rating Board (GRB) has accused MMO publishers of obstructing an investigation.
According to a report on This Is Game, The GRB wants to establish whether the in-game purchase of "jackpot items" - where the player pays a set amount in return for a random item of potentially greater value - is a form of gambling.
Ten MMO publishers were asked to provide details of similar items in their games: Neowiz, Smile Gate, CJ, WeMade, NCsoft, Actoz Soft, Mgame, NHN, Nexon, and HanbitSoft.
However, while all of the publishers have co-operated on item names, costs and virtual currencies involved in the transactions, they are refusing to provide information on payout percentages.
The publishers involved believe that the information is primarily associated with their business models, and does not fall under the jurisdiction of a ratings board.
The Korean industry is supposed to self-regulate on gambling by following a set of criteria established in 2008, but the GRB has openly questioned whether MMO publishers are still doing so.
"Game companies ask us why GRB tries to touch their business model and refuse to our request. But the jackpot item is a content of the game," said GRB chairman Soo Keun Lee.
"We don't care whatever they do outside of the game but what is matter to us is that it is a part of the game. There should have been no problem if they have followed the criteria they have made by themselves. But we doubt if they are abiding by it now. To us, it is nothing more than a dead recommendation."