LONDON  A former senior Swiss bank executive said on Monday that he had given the WikiLeaks founder, Julian Assange, details of more than 2,000 prominent individuals and companies that he contends engaged in tax evasion and other possible criminal activity.

Rudolf M. Elmer, who ran the Caribbean operations of the Swiss bank Julius Baer for eight years until he was dismissed in 2002, refused to identify any of the individuals or companies, but he told reporters at a news conference that about 40 politicians and “pillars of society” were among them.

He told The Observer newspaper over the weekend that those named in the documents come from “the U.S., Britain, Germany, Austria and Asia  from all over,” and include “business people, politicians, people who have made their living in the arts and multinational conglomerates  from both sides of the Atlantic.”

Mr. Elmer handed two computer disks to Mr. Assange at the news conference, the first significant public event the WikiLeaks founder has held since he was arrested in London in early December after Swedish prosecutors sought to have him extradited on charges of sexual crimes there. He has denied the charges but was briefly jailed last year before bail was granted.