Gates said to be under investor pressure to resign as chairman

The impending departure of Steve Ballmer as Microsoft's chief executive is not enough to satisfy some top investors who are reportedly calling for Bill Gates to resign as chairman.

Sources tell Reuters that three of the company's top 20 investors are pressing the board to force Gates out of the company he founded 38 years ago. The investors reportedly worry that Gates' presence on the board prevents adoption of new strategies and will limit the power of whoever is chosen to replace Ballmer.

While the pressure is said to come from investors who hold more than 5 percent of the company's stock, Reuters notes that the board is unlikely to entertain their suggestion. The investors' identities were not revealed.

They are also reportedly concerned that Gates maintains influence within the company that is out of proportion with his declining ownership stake. While still Microsoft's largest shareholder with nearly 389 million shares, or 4.5 percent, Gates has been selling about 80 million shares a year as he focuses on philanthropy.

The pressure comes just months after Ballmer's announcement in August that he would be stepping down as CEO within the next 12 months -- once a replacement is found who will carry out Microsoft's new vision of offering devices and services, not just software. The company's board has formed a special committee to seek out potential candidates and has been narrowing down its list of possible successors.

Gates, who stepped away from his day-to-day role at the company five years ago, was suggested by some as an early candidate to replace Ballmer. However, recent speculation has settled on Stephen Elop, a former Microsoft executive who is rejoining the company with Redmond's $7.2 billion acquisition of Nokia's handset division, and Ford CEO Alan Mulally, who has said he happy to stay at the automaker.

CNET has contacted Microsoft for comment and will update this report when we learn more.