UPDATE 3-US accuses UBS client of tax evasion, more to come

* US Justice Dept. accuses accountant of false tax filing

* South Florida U.S. Attorney says case "will not be last"

* Charge says accused tried to conceal Swiss bank account

* "Come clean now", IRS chief tells other likely offenders (Adds background, Swiss minister's comments)

By Pascal Fletcher

MIAMI, April 2 (Reuters) - U.S. authorities on Thursday arrested and charged an accountant in Florida in the first of what they said could be a series of tax evasion prosecutions of American clients of Swiss bank UBS AG (UBSN.VX) (UBS.N).

Steven Michael Rubinstein, who worked for a company in the yacht-building business, was accused of filing at least one false tax return that failed to disclose he had an account with UBS or made any money from it , the Justice Department said.

Rubinstein, an American who also had a South African passport, was arrested at his home in Boca Raton, Florida, which the charge against him says he built with the help of funds from his UBS account. A Fort Lauderdale judge ordered him to be detained pending a bond hearing scheduled for next Tuesday.

The criminal complaint filed by Internal Revenue Service (IRS) Special Agent Scott Johnson said Rubinstein's arrest resulted from information provided by UBS to U.S. authorities on the identities and account information of American clients who were using their Swiss bank accounts to evade U.S. taxes.

"Today is the first of the prosecutions resulting from that disclosure, but it will not be the last," Alexander Acosta, U.S. Attorney for the Southern District of Florida, said in the statement announcing the charges against Rubinstein.

Rubinstein's lawyer, Miami-based Robert Panoff, was not available for comment.

Acting Assistant Attorney General John A. DiCicco of the Justice Department's Tax Division said his unit was "committed to helping the IRS to ferret out and hold accountable taxpayers who are hiding assets in undisclosed foreign accounts."

Rubinstein was charged only hours after The New York Times reported that the Justice Department had opened about 100 criminal investigations into wealthy American clients of UBS, Switzerland's largest bank.

In February, UBS acknowledged responsibility for helping U.S. clients conceal assets from the U.S. government. It agreed to pay a $780 million fine and to identify some U.S. clients.

But, fearing they might get only a limited number of names, U.S. authorities are suing UBS to try to obtain identification of 52,000 undeclared accounts holding billions of dollars that they allege are held by the Swiss bank for U.S. customers.

PRESSURE ON TAX HAVENS

The arrest of the Boca Raton chartered accountant came as world leaders of the G20 nations, meeting in London, agreed to crack down on countries serving as tax havens.

But in Zurich, Swiss Economy Minister Doris Leuthard said Switzerland would keep defending its strict banking secrecy after making some concessions, but she expected more pressure on her country over the issue of tax havens.

"Because in difficult years every finance minister cares about the hair-shirt of their own tax payer, we cannot assume that we will now be left in peace," she said.

The IRS complaint accused Rubinstein of using his South African passport to open UBS accounts in the name of a nominee British Virgin Islands company, Hybridge International Ltd.

Prosecutors allege that from 2001 through 2008, Rubinstein communicated with UBS bankers about the purchase and sale of securities worth more than 4.5 million Swiss francs, moving investments from U.S. dollars to British pounds and bringing some $3 million into the United States to buy property.

"By opening the accounts in the name of the nominee entity, Steven Michael Rubinstein attempted to conceal his offshore assets and income from the IRS," the IRS affidavit said.

It added: "Each year, (he) failed to report on these tax returns any income earned on his UBS Swiss bank accounts ... (and) failed to disclose he had an interest in or a signature or other authority over a financial account in Switzerland".

UBS has argued the information sought by the United States is protected by Swiss financial privacy laws.

The IRS affidavit said Rubinstein held several face-to-face meetings with UBS bankers. "These meetings took place at various locations, including Art Basel Miami, a shopping center in West Palm Beach, (his) personal residence, and various restaurants throughout South Florida," it said.

IRS Commissioner Doug Shulman urged other Americans in the same situation as Rubinstein to give themselves up.

"Today's actions show the IRS is committed to pursuing people hiding income offshore ... It's better to come clean now instead of waiting and facing a heavier price later," he said. (Reporting by Pascal Fletcher; Additional reporting by Diane Bartz in Washington and Emma Thomasson in Zurich; editing by Tom Brown, Carol Bishopric, Toni Reinhold)