Douglas Healey for The New York Times

Federal prosecutors are expected to file criminal charges on Wednesday against Rajat K. Gupta, the most prominent business executive ensnared in an aggressive insider trading investigation, according to people briefed on the case.

The case against Mr. Gupta, 62, who is expected to surrender to F.B.I. agents on Wednesday, would extend the reach of the government’s inquiry into America’s most prestigious corporate boardrooms. Most of the defendants charged with insider trading over the last two years have plied their trade exclusively on Wall Street.

The charges would also mean a stunning fall from grace of a trusted adviser to political leaders and chief executives of the world’s most celebrated companies.

A former director of Goldman Sachs and Procter & Gamble and the longtime head of McKinsey & Company, the elite consulting firm, Mr. Gupta has been under investigation over whether he leaked corporate secrets to Raj Rajaratnam, the hedge fund manager who was sentenced this month to 11 years in prison for trading on illegal stock tips.

While there has been no indication yet that Mr. Gupta profited directly from the information he passed to Mr. Rajaratnam, securities laws prohibit company insiders from divulging corporate secrets to those who then profit from them.

The case against Mr. Gupta, who lives in Westport, Conn., would tie up a major loose end in the long-running investigation of Mr. Rajaratnam’s hedge fund, the Galleon Group. Yet federal authorities continue their campaign to ferret out insider trading on multiple fronts. This month, for example, a Denver-based hedge fund manager and a chemist at the Food and Drug Administration pleaded guilty to such charges.

A spokeswoman for the United States attorney in Manhattan declined to comment.

Gary P. Naftalis, a lawyer for Mr. Gupta, said in a statement: “The facts demonstrate that Mr. Gupta is an innocent man and that he acted with honesty and integrity.”

Mr. Gupta, in his role at the helm of McKinsey, was a trusted adviser to business leaders including Jeffrey R. Immelt, of General Electric, and Henry R. Kravis, of the private equity firm Kohlberg Kravis Roberts & Company. A native of Kolkata, India, and a graduate of the Harvard Business School, Mr. Gupta has also been a philanthropist, serving as a senior adviser to the Bill & Melinda Gates Foundation. Mr. Gupta also served as a special adviser to the United Nations.

His name emerged just a week before Mr. Rajaratnam’s trial in March, when the Securities and Exchange Commission filed an administrative proceeding against him. The agency accused Mr. Gupta of passing confidential information about Goldman Sachs and Procter & Gamble to Mr. Rajaratnam, who then traded on the news.

The details were explosive. Authorities said Mr. Gupta gave Mr. Rajaratnam advanced word of Warren E. Buffett’s $5 billion investment in Goldman Sachs during the darkest days of the financial crisis in addition to other sensitive information affecting the company’s share price.

At the time, federal prosecutors named Mr. Gupta a co-conspirator of Mr. Rajaratnam, but they never charged him. Still, his presence loomed large at Mr. Rajaratnam’s trial. Lloyd C. Blankfein, the chief executive of Goldman, testified about Mr. Gupta’s role on the board and the secrets he was privy to, including earnings details and the bank’s strategic deliberations.

The legal odyssey leading to charges against Mr. Gupta could serve as a case study in law school criminal procedure class. He fought the S.E.C.’s civil action, which would have been heard before an administrative judge. Mr. Gupta argued that the proceeding denied him of his constitutional right to a jury trial and treated him differently than the other Mr. Rajaratnam-related defendants, all of whom the agency sued in federal court.

Mr. Gupta prevailed, and the S.E.C. dropped its case in August, but it maintained the right to bring an action in federal court. The agency is expected to file a new, parallel civil case against Mr. Gupta as well. It is unclear what has changed since the S.E.C. dropped its case in August.

An S.E.C. spokesman declined to comment.

The case could be a challenge for the government. Many of the defendants convicted of insider trading, including Mr. Rajaratnam, have been caught on wiretaps swapping secret information.

At Mr. Rajaratnam’s trial, the government played a recorded conversation between Mr. Gupta and Mr. Rajaratnam in July 2008. On that call, Mr. Gupta divulged that Goldman was considering a purchase of either Wachovia or American International Group.

Evidence that Mr. Rajaratnam traded on this information was never presented, however.

Two of the most incriminating calls played in court pertained to tips that the government said had come from Mr. Gupta. But those calls were conversations between Mr. Rajaratnam and his employees, which could make them inadmissible in a trial of Mr. Gupta.

In one call played for the jury, Mr. Rajaratnam told a colleague, “I heard yesterday from somebody who’s on the board of Goldman Sachs that they are going to lose $2 per share.” In the other, Mr. Rajaratnam said to his trader, “I got a call saying something good is going to happen to Goldman.”

The S.E.C.’s original case also outlined evidence that could potentially be used at trial. That includes Mr. Gupta’s phone records of on Sept. 23, 2008. That day, the Goldman board met via telephone to consider Mr. Buffett’s $5 billion investment in Goldman.

“Immediately after disconnecting from the board call, Gupta called Rajaratnam from the same line,” the S.E.C. filing says. A minute later, Galleon funds bought more than 175,000 shares of Goldman just before the market closed, the agency says, and later netted a $900,000 profit when the deal was announced.

Though he had an enviable résumé and earned millions of dollars a year at McKinsey, Mr. Gupta became fixated on the extraordinary wealth showered on hedge fund managers and private equity chiefs, according to trial testimony. Consultants are well paid, but the compensation pales in comparison to those Wall Street titans.

Around the time of his retirement in 2007, he and Mr. Rajaratnam helped start New Silk Route, a private equity firm focused on investments in India. Though Mr. Rajaratnam never had an active role in the firm, he and Mr. Gupta were good friends, having met through their philanthropic interests.

Mr. Gupta periodically visited Mr. Rajaratnam’s hedge fund, Galleon, on Madison Avenue and 57th Street in Midtown Manhattan. The two would order Indian or Chinese takeout and kibitz in Mr. Rajaratnam’s office. Mr. Gupta became an investor in Galleon’s hedge funds.

As part of his foray into Wall Street, Mr. Gupta took a senior adviser post at K.K.R., the firm co-founded by his friend Mr. Kravis. During Mr. Rajaratnam’s trial, prosecutors played a tape of the hedge fund manager gossiping with a friend about Mr. Gupta’s ambitions.

“My analysis of the situation is he’s enamored with Kravis, and I think he wants to be in that circle,” Mr. Rajaratnam said. “That’s a billionaire circle, right?”

William K. Rashbaum contributed reporting.