NEW YORK — A Roman Catholic bishop named by Pope Francis to investigate the church’s response to clergy sexual abuse in Buffalo has himself been accused of sexual abuse of a child, an attorney for the alleged victim notified the church this week.

The attorney informed Catholic officials in New Jersey that he was preparing a lawsuit on behalf of a client who says he was molested by Brooklyn Bishop Nicholas DiMarzio in the mid-1970s, when DiMarzio was a parish priest in Jersey City, N.J.

DiMarzio said there is no truth to the accusation.

“I am just learning about this allegation,” he said in a statement Tuesday to the Associated Press. “In my nearly 50-year ministry as a priest, I have never engaged in unlawful or inappropriate behavior, and I emphatically deny this allegation. I am confident I will be fully vindicated.”

In a letter sent Monday to the church’s Newark Archdiocese, Boston attorney Mitchell Garabedian said 56-year-old Mark Matzek alleges he was repeatedly abused by DiMarzio and a second priest, the Rev. Albert Mark, now deceased, when he was an altar boy at St. Nicholas Church and a student at the parish school.

DiMarzio left Newark in 1999 to serve as bishop of Camden — a post he held until 2003, at the height of the first wave of the clergy sex abuse crisis in the United States.

Some accusers who came forward during his tenure spoke highly at the time of his willingness to listen. But victims’ groups accused DiMarzio of preaching contrition from the pulpit while challenging them at every step in court.

In 2003, the diocese settled a class-action lawsuit involving 23 accusers of Camden-area priests for $880,000, in a case that prompted the judge to scold the church for “legal hardball” tactics.

A sex abuse hotline the diocese set up under his watch connected callers directly with lawyers for the diocese instead of a victim-services advocate.

Last month, Pope Francis tapped DiMarzio to investigate the church’s Buffalo Diocese, where Bishop Richard Malone has come under fire for his handling of a burgeoning clergy abuse scandal that has prompted calls for his resignation.

“The investigation of the Diocese of Buffalo by Bishop DiMarzio is tainted because of these allegations,” Garabedian said. “There needs to be a truly neutral investigator to determine whether Bishop Malone should resign,” adding that the investigation should be led by a law enforcement agency.

Adriana Rodriguez, press secretary for the Brooklyn Diocese, said DiMarzio has completed his report on the Buffalo Diocese and submitted it to the Vatican. DiMarzio and Malone are in Rome this week for a scheduled visit of New York bishops.

Garabedian said the notice he sent to the Newark Archdiocese briefly describes Matzek’s allegations and the damage he allegedly has suffered, while seeking $20 million in compensation.

Maria Margiotta, spokesperson for the Newark Archdiocese, said it had received Garabedian’s letter and reported Matzek’s allegations to law enforcement.

Garabedian said he plans to file the lawsuit on Matzek’s behalf next month, after New Jersey opens a two-year “look back” period in which sex abuse victims will be permitted to file lawsuits without regard to the statute of limitations, which typically limits the amount of time in which an alleged victim may file suit.

DiMarzio completed his review of the Buffalo Diocese, known as an “apostolic visitation,” last month. He said he made three trips to the diocese over seven days and interviewed nearly 80 clergymen and parishioners.

Staff writer Jeremy Roebuck contributed to this article.

This story has been corrected to reflect that the first name of the bishop of Buffalo is Richard, not Joseph.