At least 231 children at a famous boys’ choir school in Germany were victims of physical abuse, according to a lawyer tasked by the Catholic institution with investigating allegations, giving a far higher figure than thought for the scandal, which dates back decades.

The Regensburger Domspatzen, a 1,000-year-old choir in Regensburg, Bavaria, was dragged into the massive sexual abuse scandal plaguing the Catholic church in 2010 when allegations of assaults that took place several decades ago went public.

The choir was run by Pope Benedict’s elder brother, Georg Ratzinger, from 1964 to 1994 when most of the claimed abuses took place.

Ratzinger has said that the alleged sexual abuse was “never discussed” in the time that he ran the choir attached to the boarding school.

A bridge across river Danube, in front of the Regensburg cathedral. Photograph: Diether Endlicher/AP

Lawyer Ulrich Weber, who had been commissioned by the diocese to look into the cases, said at a press conference on Friday that his research, which included 70 interviews with victims, uncovered abuse that took place from 1945 to the early 1990s.

“I have here 231 reports of physical abuse,” he said.

These ranged from sexual assault to rape, severe beatings and food deprivation, said Weber.

“The reported cases of sexual abuse in Regensburg were mostly concentrated in the period of the mid to late 1970s,” he said, adding that 50 victims spoke of 10 perpetrators.

The director and composer Franz Wittenbrink, a former pupil of the boarding school, had told Spiegel magazine in 2010 that there was a “system of sadistic punishments connected to sexual pleasure”.

The German scandal is one of several to have rocked the Catholic church in recent years, notably in Ireland where one priest admitted sexually abusing more than 100 children.

Several German institutions have also been engulfed by the scandal, including an elite Jesuit school in Berlin, which admitted to systematic sexual abuse of pupils by two priests in the 1970s and 1980s.

Most of the priests concerned are not expected to face criminal charges however, because the alleged crimes took place too long ago.

But there have been calls for a change in the law and for the church to pay compensation to victims.

In February last year, the Regensburg diocese said there were 72 victims of abuse, and offered compensation of €2,500 each.