SAN FRANCISCO: Yahoo Inc is seeking to conceal large portions of a shareholder lawsuit alleging the Internet company’s board improperly thwarted Microsoft Corp’s $47.5 billion takeover offer, raising shareholder questions over the motives for the secrecy.

In a letter sent Friday to the judge overseeing the case in Delaware, a lawyer for the shareholders argued Yahoo is trying “to whitewash embarrassing documents” because the company thinks the information will damage the board’s efforts to repel a challenge by activist investor Carl Icahn.

Angered by the board’s handling of Microsoft bid, Icahn has nominated an alternate slate of candidates to oppose Yahoo’s 10 current directors — including Chief Executive Jerry Yang — at the Sunnyvale-based company’s July 3 annual meeting.