A Bay Shore doctor pleaded not guilty Friday in federal court in Central Islip to charges of conspiracy, health care fraud and income-tax evasion, according to officials. Frank Lobacz, who also has offices for his family practice in Brentwood, was accused of filing $800,000 worth of false claims with health insurance programs, including Medicare, and evading more than $1 million in income taxes. Assistant U.S. Attorney Allan Bode said in court papers that Lobacz had failed to pay almost $1.3 million in taxes from 2001 to 2003. Lobacz's attorney, Barry Pittman of Bay Shore, said the government had charged Pittman a year ago only with income-tax evasion, but added new charges Friday because the original case could not stand up. Pittman said much of the supposed health fraud involved legitimate bills run up by his clients' relatives. Bode declined to comment. U.S. District Court Judge Denis Hurley released Lobacz pending more hearings.