Cost-per-action advertising, which contributes up to a third of the FarmVille and Mafia Wars maker's revenues, removed until Zynga can control its implementation itself.

Zynga had been under fire from web business blog TechCrunch for featuring CPA advertising for subscriptions to mobile phone information services, which contravened Facebook's terms and conditions because, masquerading as such playthings as IQ quizzes, they did not clearly state the player is required to start a $10-$20 service subscription to take part.

New game FishVille, which featured CPA advertising, was taken down by Facebook only two days after its launch, but was reinstated at 12.00am PST today, It is thought to have triggered Zynga's decision.

Zynga CEO Mark Pincus claimed on his blog that the company had not been able to control the ads that its games were serving to players because they're instead managed by the offer companies with which it works. 

"We recognize it is our responsibility to ensure that offers which generate a bad user experience are not shown with any of our games," he said. "Therefore, we are removing all CPA offers across Zynga games until we can control their inclusion and presentation ourselves."

TechCrunch reports that Zynga makes a third of its revenues from commercial offers such as CPA advertising.