Einhorn Fires Back at Apple's Tim Cook

Kimihiro Hoshino | AFP | Getty Images

The battle between Apple and David Einhorn got more heated after the fund manager responded to comments made by CEO Tim Cook early Tuesday.

Apple's Cook called Einhorn's lawsuit against the tech giant a "silly sideshow" at the Goldman Sachs Technology and Internet Conference and Einhorn's firm, Greenlight Capital, quickly fired back.

(Read More: Apple's Cook Calls Einhorn Lawsuit 'Silly Sideshow' )

"If Apple thinks the lawsuit is a waste of resources it could simply end the matter by complying with existing law and filing a new proxy that unbundles the proposed changes to the charter so that shareholders can express their views on each matter separately," a Greenlight spokesperson said in a statement Tuesday.

(Read More: Apple Pushes Back Against Einhorn Allegations of Cash Hoarding )

Einhorn, fund manager for Greenlight Capital, accused Apple of cash hoarding earlier last week and is encouraging shareholders to vote against Apple's proxy because he thinks proposition two will kill the option of Apple issuing preferred stock.

However, Glass Lewis, one of the most prominent proxy advisory firms in the world, publicly took sides with Apple in the debate.

(Read More: Live Blog: Cook Says Apple Does Not Have 'Depression Era Mentality' )

The firm said Tuesday that it supports Apple's proposition two and is against David Einhorn's recommendations for cash distribution.

Glass Proxy joins ISS, the largest proxy advisory firm in the world, in supporting Apple.

(Read More: Apple? Einhorn Just Doesn't Get It: Cramer )

Apple's proposition two basically would make it so that Apple could issue preferred stock, but only with the approval of shareholders.

"If Proposal #2 is adopted, our shareholders would have the right to approve the issuance of preferred stock. As such, Proposal #2 has the support of many of our shareholders," the company said in a statement last week.