Social games giant Zynga has suffered another high-profile executive departure, with chief marketing officer Jeff Karp resigning yesterday.

Reuters notes that Karp joins chief operating officer John Schappert and chief creative officer Mike Verdu as top executives who have quit since August.

The world's largest social games maker, and the company behind popular Facebook games such as Farmville, has shed almost three-quarters of its market value since a much-heralded public debut in December.

Zynga, which is struggling to staunch growing losses of users, was one of several consumer Internet companies that listed on stock markets to much fanfare in late 2011. In July it reported a net loss for its second quarter and cut its full-year earnings per share forecast, news that resulted in shareholder lawsuits against the company.

Zynga has made a number of acquisitions in the mobile market, as it looks to diversify beyond its core business of creating games for the Facebook platform, but CEO Mark Pincus recently warned that the firm is “wary” of investing heavily in the mobile games space, stating that the industry has not reached the “all-in, confident moment” where it becomes a safe bet. It also recently announced a mobile developer partner programme, to boost its position in this market.