They were sent to school to acquire knowledge and be better people but instead they were subjected to both sexual and physical abuse.

At least 547 boys at a German Catholic choir school suffered sexual or physical abuse in what victims have likened to "prison, hell or a concentration camp", said an investigator.

The revelation has been termed one of Germany's worst such scandals.

The Regensburger Domspatzen ("Cathedral Sparrows"), a 1,000-year-old cathedral choir in the southern state of Bavaria, was in 2010 dragged into the massive sexual abuse and paedophilia scandal plaguing the Catholic Church around the world.

Many victims remembered the world-famous choir school in the town of Regensburg as "the worst time of their lives, marked by fear, violence and helplessness", said lawyer Ulrich Weber, who was commissioned two years ago by the diocese to look into the cases.

Presenting his final report on abuses between 1945 and the early 1990s, Weber said he had uncovered 67 cases of sexual abuse and 500 cases of other physical violence, with some former singers having fallen victim to both.

This more than doubled the 231 reported abuse cases by school clergy and educators which Weber had uncovered through interviews by January 2016, when he said victims had spoken of rape, sexual assaults, severe beatings and food deprivation.

Weber, who was not able to speak with all former students, said he estimated the true number of victims at around 700.

The investigator pointed to a "culture of silence" that aimed to protect the reputation of the renowned choir of boys and young men that has made many recordings and performed around the world.

He placed part of the blame for the situation on the school's former choir master George Ratzinger, the elder brother of former pope Benedict XVI.

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.