NEW YORK, June 19 (Reuters) - A former Sullivan & Cromwell partner who was sentenced to more than two years in prison for not paying taxes was suspended Tuesday from practicing law in New York.

The New York Appellate Division, First Department, suspended John O'Brien after finding he had committed a "serious crime" in failing to pay $2.5 million in taxes while he was a partner at Sullivan & Cromwell. A federal court in Manhattan sentenced O'Brien in January to 28 months in prison after he pleaded guilty to four criminal misdemeanor charges.

The appellate court directed O'Brien to appear before departmental disciplinary committee within 90 days of his release from prison and issue a report stating why a final order for censure, suspension or disbarment should not be entered, according to the order.

New York law provides for the automatic disbarment of lawyers convicted on felony charges. While O'Brien was instead convicted on misdemeanor charges, the First Department said two of those counts "fall squarely" into the definition of a serious crime, which can include willfully not filing income tax returns.

Hal Lieberman, a lawyer for O'Brien at Hinshaw & Culbertson in the disciplinary case, did not respond to requests for comment. A court-appointed lawyer for O'Brien in his criminal case, Nicholas Pinto, declined comment.

O'Brien, 49, is currently serving his time in the Metropolitan Detention Center in Brooklyn, New York, according to the Federal Bureau of Prisons. He is scheduled for release in March 2014.

He is appealing his sentence to the 2nd Circuit Court of Appeals. In a filing June 5, a lawyer for O'Brien said he was primarily seeking resentencing before a different judge. He had been sentenced by U.S. Magistrate Judge Henry Pitman in Manhattan.

"If that relief is granted, we will urge the district court to impose a sentence that does not entail incarceration," Pinto wrote.

Prosecutors in a brief Monday urged the 2nd Circuit not to expedite to appeal, saying the request does not raise substantial questions that would reduce O'Brien's sentence. Lawyers with the U.S. Attorney's Office in Manhattan said in the brief that O'Brien's 28 month sentence is below the 37 to 46 months recommended by the federal sentencing guidelines.

A previous court-appointed lawyer for O'Brien, Russell Neufeld, sought Feb. 10 to be relieved from the case because of "strong disagreements" about the merits of his appeal, the brief said. Pinto was appointed after Neufeld's request was granted. Neufeld did not respond to a request for comment.

O'Brien, who had earned $10 million during the tax years at issue, claimed not to have the funds to cover the appeal after the court approved Neufeld's request. O'Brien said he had $2.08 million in debt, excluding penalties to the Internal Revenue Service, and monthly expenses of $3,720.

The filing stated he earned $183,000 a month until May 2009, when he was still a partner at Sullivan. He said he had received $98,187 in the last year from his Sullivan & Cromwell pension and had property in Canada Lake, New York, worth $281,400.

A spokeswoman for Sullivan & Cromwell did not respond to a request for comment.

The case is In the Matter of John J O'Brien, New York State Supreme Court Appellate Division, First Department, No. 1555.

For the Departmental Disciplinary Committee: Jorge Dopico and Raymond Vallejo.

For O'Brien: Hal Lieberman, Hinshaw & Culbertson.

(By Nate Raymond)

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