NEW BEDFORD - A former Bristol County prosecutor, already charged with sexually assaulting a 17-year-old girl in Attleboro District Court, is now accused of having an earlier relationship with a 30-year-old defendant in return for his influence in her case.

The new allegations against the former prosecutor, Peter Joseph Costanza, 39, are part of an eight-count grand jury indictment in New Bedford Superior Court, where Costanza pleaded innocent Wednesday.

The indictment includes the sexual assault and attempted extortion charges related to the 17-year-old girl he is accused of groping in Attleboro District Court and intimidating a witness and public corruption charges related to the earler alleged victim when Costanza was an assistant district attorney in New Bedford.

The woman was facing criminal charges in New Bedford District Court where Costanza, of New Bedford, worked before being transferred to Attleboro District Court in the spring.

"They began a personal relationship in return for him influencing her case," said Bridget Norton Middleton, a spokeswoman for the Plymouth County District Attorney's Office, which is handling the case to avoid the appearance of a conflict of interest. The relationship occurred beginning May 24, 2006, and continued to June 15, 2008, said Middleton, who would not be more specific.

She declined to say what charges the woman faced and did not disclose the outcome of the case.

Costanza was the supervising assistant district attorney in Attleboro District Court when he was arrested Aug. 3 for allegedly groping the 17-year-old girlfriend of a defendant he was prosecuting.

Prosecutors say the incident occurred Aug. 1 in a conference room between the main courtroom and the district attorney's office, and was reported to court officials and police the same day.

The girl told investigators Costanza told her he had a "lot of power in this courthouse."

The 30-year-old woman in the New Bedford case contacted authorities after Costanza's arrest in the Attleboro case, authorities said.

Costanza is free on $10,000 cash bail. Neither he, nor his lawyer, Daniel W. O'Malley, of Quincy, would comment on the indictment.

Costanza was suspended without pay following his arrest, but has since been fired, according to Gregg Miliote, spokesman for Bristol County District Attorney Sam Sutter.

Costanza, a lawyer since 2002, was a prosecutor in New Bedford District Court before being promoted last April and transferred to Attleboro District Court to supervise other prosecutors in the office.

In August, when Costanza was arraigned in Attleboro District Court, O'Malley said his client had a "stellar" record as a prosecutor and was stunned by the allegations against him. He is due back in superior court for a pretrial conference Nov. 21.