MINNEAPOLIS - The head of the Archdiocese of St. Paul and Minneapolis announced Tuesday that he is stepping aside from public ministry effective immediately after an allegation that he inappropriately touched an underage boy on the buttocks during a public photo session.

In an open letter posted on the archdiocese’s website, Archbishop John Nienstedt denied the allegations but said he would remove himself from ministry pending a police investigation.

Nienstedt said he learned of the allegation over the weekend. He said it came from a young man whom Nienstedt had anointed in the Sacrament of Confirmation in 2009. Nienstedt said he doesn’t know who his accuser is, but said the young man alleged that Nienstedt inappropriately touched him during a public photo session after the confirmation ceremony.

“I presume he is sincere in believing what he claims, but I must say that this allegation is absolutely and entirely false,” Nienstedt wrote. “I have never once engaged in any inappropriate contact with a minor.”

Nienstedt said he normally stands for these photos with one hand on his staff and the other hand either on the right shoulder of the newly confirmed person, or on a stole that hangs from his chest.

“I do that deliberately, and there are hundreds of photographs to verify that fact,” he wrote.

The archdiocese said in a statement that it learned of the allegation last week and instructed the person who brought it forward to go to police. The archbishop decided to step aside from public ministry after consulting with the Holy Father’s ambassador to the United States, the statement said.

Auxiliary Bishop Lee Piche will cover Nienstedt’s duties during the investigation, which Nienstedt said he hoped would be thorough but quick so he could return to work.

Nienstedt has been under fire in recent months over allegations that he and other church leaders mishandled cases of clergy sexual misconduct, and there have been calls for him to resign from leadership. Earlier this month, a court ordered the archdiocese to release the names of nearly three dozen priests who had been credibly accused of sexually abusing minors.

Nienstedt also has hired a firm to review all clergy files and has convened a task force to examine the way church officials have handled accusations of sexual misconduct.

On Sunday, Nienstedt spoke during two Masses at a suburban Minneapolis church, telling parishioners: “I am here to apologize for the indignation that you justifiably feel. You deserve better.”

Front Section, Pages 2 on 12/18/2013