A government prosecutor charges that John Peter Galanis, linked to a number of fraudulent Utah ventures, is the head of "a thoroughly corrupt criminal organization that defrauded investors, banks and the government out of tens of millions of dollars."

The comments by Assistant U.S. Attorney Vincent L. Briccetti came at the opening of a federal trial in White Plains, N.Y., in which Galanis and three co-defendants are charged with fraud, conspiracy and racketeering in connection with the sale of limited-partnership tax shelters involving oil- and gas-drilling ventures between 1981 and 1983.The deals, according to the government's case, involved $50 million in investor funds and $172 million in fraudulent tax write-offs.

Galanis, 44, once the driving force behind a multimillion-dollar Atlantic City development deal, is charged with fraud involving drilling operations basedin Salt Lake City and is to be tried later this year in a New York state court on fraud and conspiracy charges in connection with real estate syndication dealsinvolving hundreds of luxury condominiums in Utah, Florida, Illinois, Arizona, California and Louisiana.

In the White Plains case, Galanis and seven associates face charges of racketeering, securities fraud and tax fraud in connection with the syndication of a series of allegedly fraudulent limited-partnership tax shelters involving oil- and gas-drilling ventures by a company called Transpac Oil & Gas of Salt Lake City. Four of the associates subsequently pleaded guilty and are expected to testify for the government.

The charges outlined by Briccetti Tuesday stem from a 58-count grand jury

indictment returned in September in the Southern District of New York federal court following a two-year government.

Galanis was described in the indictment as the "undisclosed principal" behind an organization that sold and promoted the tax-shelter deals. It also charged that Galanis and his associates bribed officials of a New York state bank and carried out the fraudulent takeover of banks in Utah and Connecticut and three mutual funds in California.

Galanis, who also has been charged with fraud in connection with Atlantic City's failed Boardwalk Marketplace development, sat quietly with his co-defendants at a table in the front of the courtroom as Bric-cetti detailed the government's allegations for the jury.

Briccetti described Galanis as the boss of "an organization whose modus operandi was fraud, whose very activities were corrupt and whose appetite for money was voracious."

Although Galanis' name did not appear among the officers of any of the companies involved in any of the various business deals, Briccetti said, "everyone answered to John Galanis, and there was no doubt he was the boss." Galanis has vehemently denied those allegations, contending that he was only a consultant, that there was no fraud and that government investigators simply do not understand the business transactions.

His attorney, Brian Barrett, hammered away at those same issues in his opening statement.

Barrett said there was no racketeering and no "Galanis organization," as the government has charged.

"He does financing," Barrett said of Galanis. "He understands it, he's brilliant at it. . . . He breaks no laws at it."

"We're not talking about a morality play here," Barrett said at another point, acknowledging that Galanis had a flamboyant and excessive lifestyle. "We're talking about business transactions designed to make money."

The trial before U.S. District Judge Charles Brieant is expected to last six to eight weeks, and Galanis hinted Tuesday that he might take the stand in his own defense.

Galanis is scheduled to be tried later this year in a New York state court in Manhattan on fraud and conspiracy charges related to Boardwalk Marketplace and another failed real estate syndication deal involving hundreds of luxury condominiums in Utah, Florida, Illinois, Arizona, California and Louisiana.

Boardwalk Marketplace was a plan to redevelop a three-block area near Atlantic City's Boardwalk casino strip into a commercial and tourist center by renovating a dozen hotels and surrounding them with new shops, boutiques and restaurants. Investors from across the country put $75 million into nine limitedpartnerships before the project collapsed in bankruptcy in June 1986.

Standing trial with Galanis are Anthony Marchese, 47, of Southport, Conn., who served as a financial and banking consultant for several of the companies allegedly involved in the swindle; Samuel Rosengarten, 66, of Armonk, N.Y., allegedly the head of Galanis' nationwide sales organization, and Arthur Mason, 46, a Washington, D.C., lawyer allegedly involved in Galanis' takeover of a federal savings bank in Westport, Conn.

Laurence Klusky, a co-defendant and accountant, pleaded guilty to conspiracy and tax-fraud charges and agreed to cooperate with the government andtestify against Galanis. Ronald Williams, a Texas lawyer, also has pleaded guilty.