Research conducted by trade groups including the Entertainment Software Association has shown that over 9.78 million games were successfully downloaded illegally during the month of December.
However, the actual number of illegally downloaded games is expected to be much higher, with the ESA admitting that its survey only focused on 200 games accessed on the most popular peer-to-peer platforms such as BitTorrent, eDonkey, Gnutella and Ares.
"These figures under-represent the true magnitude of online game piracy," said the ESA. "They address only downloads of a small selection of ESA member titles.
"And while they account for illegal downloads that occur over select P2P platforms, they do not account for downloads that occur from 'cyberlockers' or 'one-click' hosting sites, which continue to account for high volumes of infringing downloads."
The countries with the heaviest number of unauthorised games downloads by volume were Italy (20.3%), Spain (12.5%), France (7.5%), Brazil (6%) and China (5.7%).
"ESAs reporting demonstrates a strong correlation between countries that lack sufficient protections for technological protection measures and countries where online piracy levels for entertainment software are high," said the body.
The research was conducted with the International Intellectual Property Alliance (IIPA), which has filed its findings with the United States Trade Representative (UTSR).
The report recommends that 35 countries be placed on a 'priority watch list', including Canada, Brazil and Mexico, due in large part to inadequate response to regional piracy problems. The UTSR could impose sanctions on some of the countries named.
Spain is another country which the ESA and IIPA recommended is placed under "close scrutiny" due to the recent decriminalisation of infringements via peer-to-peer networks.