Billionaire investor Carl Icahn is once again on the offensive, attacking eBay’s board of directors in an open letter over what he sees as a conflict of interest.

In the letter, Icahn specifically singles out directors Marc Andreessen and Scott Cook as appearing to be “value driven for themselves, personally profiting while costing eBay stockholders at least $4 billion.”

Icahn took Cook to task for his investment and advisor role at payment processing company intuit, a firm Icahn says is eBay’s direct competitor. Cook owns nearly $1 billion in Intuit stock. The company has a product called GoPayment that Icahn says is “identical” to PayPal Here.

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“Is it good for PayPal to have a competitor in the board room gaining insights into its operations, product pipeline and proprietary technologies?” Icahn asks facetiously.

In the letter, the business mogul also questions a deal in which eBay sold its controlling stake of Skype to Andreessen and venture capital firm Silver Lake for $1.9 billion only to see it sold to Microsoft 18 months later for $8.5 billion. Icahn says that $4 billion gain should have gone to eBay’s shareholders and not into Andreessen and Silver Lake’s pockets.

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“It is very say to us that [eBay CEO] Mr. [John] Donahoe appears to lack awareness about what is going around him on his board and in the marketplace,” Icahn added on Monday.

For months, Icahn has insisted that the company split its online auction business from its PayPal payment service to restore credibility in the boardroom.

“We believe corporate governance at Ebay is dysfunctional," Icahn says. “Vote in favor of our precatory proposal in order to send a clear message to the eBay Board that eBay and PayPal must be separated -- NOW.”

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