July 16, 2008 -- Hundreds of rich Americans whose names and secret foreign bank account information were turned over to US tax authorities could face criminal prosecution. A Senate committee is scheduled to convene tomorrow and among those called to testify are foreign bank account holders, including one of the wealthiest men in Los Angeles.

48 year-old Peter Lowy and his family own the giant Westfield shopping center fortune and will control the retail space in the rebuilt World Trade Center in New York. Bob Bennett, a lawyer for Lowy, who is a prominent contributor to both Democratic and Republican candidates, told ABC News that Lowy's name was on the list of secret accounts from a Liechtenstein bank but that Lowy did nothing wrong.

Bennett said Lowy is out of the country tomorrow and will not be available to testify.

For years, the LGT Bank in the tiny European principality of Liechtenstein, tucked between Austria and Switzerland, has been regarded as a safe haven for wealthy Americans trying to hide their money from the IRS. It helps that the reigning prince there, Hans-Adams II, and his family own the bank and strictly enforce the country's bank secrecy laws.

"Liechtenstein is regarded as one of the most secretive places in the world," said John Christensen of the London-based Tax Justice Network.

But all that changed when a disgruntled computer technician at LGT, Heinrich Kieber, downloaded all the names and secret accounts on to two CDs and turned them over to tax authorities in the US and Europe.

"It completely exposed the fact that Liechtenstein is nothing but a place to hide your money from tax collectors, and any other police who might be interested," said Kieber's Washington-based attorney Jack Blum. Kieber is now wanted in Liechtenstein for violating bank secrecy laws there, but his attorney says it is the tax cheats that are the real criminals.

"They are the people who are taking advantage of the rest of us, who are withholding and paying," said Blum. "They're the crooks."

LGT Bank says that while the Royal Family does own the bank it does not "operate" the bank. While LGT did decline to have officials testify before the Senate committee, they say they did provide a "compliance" officer who answered questions from Senate staffers for nearly ten hours last Friday. (click here to read the full statement from LGT Bank)

Also called to testify tomorrow are current and former officials of the giant Swiss bank UBS, including the head of the private wealth management Americas office, Martin Liechti, who was briefly detained by US authorities in Miami in May.

In court documents, federal prosecutors say UBS bankers helped set up many of the secret accounts in Liechtenstein and, overall, hid as much $20 billion belonging to US citizens.

"Sums are enormous and UBS appears to have been particularly aggressive in the way they marketed their activities in the US and elsewhere," said Christensen. "So UBS is extremely vulnerable to losing their license in the US."

One UBS banker, Bradley Birkenfeld, pleaded guilty last month and admitted to smuggling cash and diamonds for Americans trying to hide their wealth from the IRS.

In federal court documents obtained by ABC News, federal prosecutors allege that Birkenfeld's bank trained bankers traveling to the US in "techniques to avoid detection" by law enforcement authorities, "including training bankers to falsely state on customs forms that they were traveling into the United States for pleasure and not business".

Prosecutors say part of the Swiss bank scam was for the bank managers to have a third party who would set up sham entities for the US clients in tax havens, such as Panama or the British Virgin Islands, and pose as the owners of the entities.

"By concealing the US clients' ownership and control in the assets held offshore," the prosecutors say the Swiss bank and its managers "defrauded the IRS and evaded United States income taxes." (click here to read more of the court documents)

"The Americans were probably very shocked when their information wound up in the hands of the Internal Revenue Service," said Blum.

Click Here for the Investigative Homepage.