Yahoo’s largest outside investor has stepped up its attack on the company’s top officials, calling again for Yahoo’s board of directors to fire chief executive Scott Thompson for listing a nonexistent degree among his academic credentials.

Thompson, who joined the company in January, apologized to Yahoo employees on Monday for misstating that he held a computer science degree in his corporate biography and Yahoo federal filings .

In a letter to the board Wednesday, the Third Point hedge fund wrote: “Mr. Thompson's ‘apology’ was clearly insufficient and it seems that the only thing he actually regrets is that he has been caught in a lie and publicly exposed. Without any explanation or accountability, Yahoo! has been left to flounder under a discredited leader for an undefined period.  So, after six days, we must ask – what is this Board waiting for?”

Third Point, led by chief executive Daniel Loeb, has been locked in a proxy battle with the Web giant. Loeb was the first to bring attention to Thompson’s misleading résumé. He also questioned the academic credentials and leadership of Yahoo board member Patti Hart, who headed the search committee that ultimately hired Thompson. Yahoo announced Tuesday that Hart would not seek reelection to the board.

After confirming that Thompson held only an accounting degree, Yahoo launched an investigation to review the CEO’s academic record.

In Wednesday’s letter, Loeb demanded that that Thompson and Hart be replaced immediately with nominees that the hedge fund recommended for the board, and that a Third Point nominee lead the next CEO search committee. Loeb also said that the company should appoint an interim CEO immediately, suggesting either Yahoo chief financial officer Tim Morse — who served as interim CEO earlier this year — or Global Media head Ross Levinsohn.

“This is the only way for Yahoo! to move past this embarrassing episode,” the letter said.

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