A 62-year-old Manhattan meat magnate who served between May 2003 and February 2007 as the chairman of the New York County Republican Party and who was appointed by Governor Pataki to the board of Cornell University and as chairman of the Hudson River Park Conservancy is pleading guilty to a felony charge of tax evasion.

The guilty plea, the result of an investigation by the district attorney of New York County, Robert Morgenthau, is the latest blow to the Republican Party in New York City. Its top public officeholder, Mayor Bloomberg, resigned from the party to become an independent earlier this year, and for the first time in more than a decade, Republicans hold no statewide offices.

James Ortenzio, who lives in the West Village, also pleaded guilty to a misdemeanor charge of violating the Public Officers Law.

The plea resulted from a probe by the Manhattan district attorney into the Cipriani restaurant company, for whom Ortenzio was a meat supplier. Last month, two members of the Cipriani restaurant family, Arrigo and Giuseppe Cipriani, were sentenced to pay $10 million in back taxes.

The investigation began in November 2005 after Mr. Morgenthau’s office received an anonymous letter outlining, in what is now known to be accurate detail, the inner workings and relationship of the Ciprianis and the Hudson River Park Trust, a spokesman for the office, Barbara Thompson, said yesterday.

The charges stem from work in 2004 when Ortenzio received $100,000 for a consulting job for Fisher Brothers, a real estate holdings company. Mr. Morgenthau charged that Ortenzio “intentionally” omitted the income when he filed the annual financial disclosure statement with the New York State Ethics Commission, which is required for public officers and high-ranking party officials.

In 2005, Ortenzio also failed to report on state tax returns $80,000 that he received for arbitrating a dispute in 2004 between two competing helicopter flight services in the city, Air Pegasus of New York Inc. and Sightseeing Tours of America Inc., according to the charges. The companies were both located on land belonging to the Hudson River Park Trust when he was chairman.

An attorney for Ortenzio, Randy Mastro, said his client “made a mistake.”

“It’s perfectly legal for him to receive a consulting fee, there was no issue about that,” Mr. Mastro said. “He should have disclosed the fee on the public disclosure form.”

According to his plea, Ortenzio faces five years probation, must pay a $50,000 fine, and must file amended, accurate tax returns for 2004 and 2005. He will be sentenced on January 9.

Ortenzio has substantial holdings in several meat-processing companies and was a major distributor to Cipriani restaurants, Mr. Morgenthau said.

From 1999 to 2003, Ortenzio served as the chairman of the Hudson River Park Trust, an organization that created Hudson River Park in 1998 and stretches five miles along Manhattan’s shoreline from Battery Place to 59th Street.

Ortenzio’s reputation as a powerful city figure came from the wholesale food industry and meat market empire he built in the Meatpacking District in the 1980s and early 1990s. He has commercial and residential real estate holdings throughout Manhattan, his attorney said.

Governor Pataki appointed him to the Board of Trustees at Cornell University in 1995, and, in 1996, he was named chairman of the Hudson River Park Conservancy, which was then part of the Empire State Development Corporation. His public service jobs were all pro-bono, Mr. Mastro said.

“In the ledger of life, while he’s acknowledged these mistakes, they have to be viewed in the context of all the good he’s done in his life,” Mr. Mastro told The New York Sun. “That good, that public good far outweighs the mistakes he’s made.”