NEW YORK — A former board member of Goldman Sachs and Procter & Gamble pleaded not guilty Wednesday to federal charges accusing him of acting as “the illegal eyes and ears in the boardroom” for a friend who was already convicted in the biggest insider trading case in history. The case, built partially on use of wiretaps for the first time in insider trading, stands to offer unprecedented insight into allegations of greed at the highest levels of Wall Street.

The indictment unsealed Wednesday accuses Rajat Gupta of cheating the markets with Raj Rajaratnam, the convicted hedge fund founder who was the probe’s prime target.