WASHINGTON - US senators lashed out at federal prosecutors on Wednesday for a lack of zeal in going after Swiss banks that helped Americans dodge taxes, blaming both sides for billions of dollars in missed revenues.

The Senate Permanent Subcommittee on Investigations this week alleged new misdeeds by Switzerland's Credit Suisse, citing secret meetings in luxury hotels and hidden elevators one senator said belonged in a spy novel.

But the senators saved some their harshest criticism for two Justice Department officials who testified at the hearing after a morning session with bankers.

"You have been incredibly slow over a five-year period," said Arizona Senator John McCain, referring to the moment that Swiss bank UBS admitted to helping US clients hide money from the tax man and handed over their names.

"You're doing a job that, frankly, has not shown any progress. ... The taxpayers' dollars are not well spent by the way you and your organization," said McCain, the highest ranking Republican on the committee.

The Justice Department is probing 14 Swiss banks over taxes after UBS became the first major bank to settle over the charges. Two smaller Swiss banks have had to close shop as a result of the US investigation.

In a lengthy report this week, the senators said Credit Suisse bankers secretly traveled to the United States, sometimes on tourist visas, describing one customer who got bank statements tucked into the pages of an issue of Sports Illustrated magazine at a hotel meeting.

The report said Credit Suisse opened accounts for more than 22,000 US customers, with combined assets of $12 billion. The bank has accepted responsibility for wrongdoing by its staff.

Switzerland has amassed assets worth trillions of dollars from foreigners over the past decades, aided by its tight bank secrecy laws, but the business has come under threat from politicians and regulators abroad.