The indictment is the second in the case. In May, Bradley C. Birkenfeld, an American who was a senior private banker at UBS, was accused of helping a UBS client evade taxes through undeclared offshore accounts. He pleaded guilty in June and is cooperating with prosecutors in their investigation. Mr. Birkenfeld is expected to be sentenced to in January.

The offshore banking services brought in annual revenue of $200 million before UBS said it shut them down this year.

Mr. Weil, who turns 49 on Thursday, was the head of UBS’s wealth management business, which included the United States cross-border business now under scrutiny. He was promoted in July 2007 to chief executive of a UBS division that oversaw the United States cross-border business and worldwide private banking.

The bankers, managers and desk heads identified as co-conspirators helped American clients hide assets by preparing forms called W8-BENs that made it look as if offshore entities, and not the clients, held the assets. The clients also failed to file I.R.S. disclosure forms that are required if they have an interest in foreign financial accounts worth more than $10,000.

One unnamed manager referred clients in 2000 to outside lawyers and accountants to set up illegal offshore entities with UBS. Another manager told clients worried about being caught by the I.R.S. that UBS “would not be pressured” to disclose clients’ identities.

Mr. Weil, the indictment said, referred to the private banking business he oversaw as “toxic waste,” because he knew that UBS was flouting United States tax and securities laws as well as a special agreement between the bank and the I.R.S. Mr. Weil, the indictment said, instructed bankers to expand the private banking business even as it was coming under federal scrutiny.

Letters reviewed by The New York Times in August showed that senior executives were alerted at least three years ago to possible violations of securities laws in dealings with American clients of its private bank. The letters cast a spotlight on the senior executives who were copied on them, including Marcel Rohner, who led the bank’s global wealth management unit and has been chief executive since 2007, and Peter Kurer, the bank’s former top lawyer, who is now its chairman.