Rudolf Elmer, a former employee of Swiss-based Bank Julius Baer, said the account holders include "high net worth" celebrities, business leaders and lawmakers from the U.S., Britain and Asia.
Special Report: WikiLeaks
WikiLeaks founder Julian Assange appeared alongside Elmer at London's Frontline Club to collect the files, and praised the ex-banker's attempts to expose alleged shady practices in the financial industry.
Assange said that, with his organization focused on the publication of its cache of about 250,000 diplomatic cables, it could be several weeks before Elmer's files are reviewed and posted in the WikiLeaks website. "We will treat this information like all other information we get," Assange said. "There will be a full revelation."
Elmer, who has previously leaked banking documents to the secret-spilling site, told journalists that he wanted to expose the offshore banking system. "I want to let society know how this system works," he said. "It's damaging society."
His decision to release the new files to WikiLeaks comes two days before he is due to appear before a Zurich regional court to answer charges of coercion and violating Switzerland's strict banking secrecy laws.
Elmer said he would not reveal what specifically was in the documents, and said that he personally would not disclose "individual companies or individual names" of the account holders.
Assange has made few public appearances since he was released on bail on Dec. 16 following his arrest on a Swedish extradition warrant.
Under the terms of his release, Assange must live at the mansion home of Vaughan Smith, the owner of the Frontline Club. He was compared the regime to "high-tech house arrest," but has recently promised that the flow of leaked documents published by his organization would increase.
Last week, Assange said that WikiLeaks would.
WikiLeaks sparked an international uproar with the publication of hundreds of classified U.S. diplomatic cables late last year, revelations that caused weeks worth of embarrassing news stories for the U.S. and its allies. But the flow of leaks, published in The New York Times, The Guardian, Der Spiegel, Le Monde and El Pais, has slowed recently amid a barrage of online attacks,and the Swedish prosecution of Assange for alleged sex crimes.
The Swedish case has divided world opinion. Assange and his supporters say he is being prosecuted for political reasons, something denied by Swedish authorities and Assange's alleged victims, who insist it has nothing to do with WikiLeaks' activities.
CBS News producer Steve Berriman reports Feb. 7 was set as the date for Assange's full hearing, and the judge decided Tuesday to relax the restrictions governing his house arrest for Feb. 6 and 7, to allow him to stay in London the night before his next appearance.