Former Vatican doctrinal chief Cardinal Muller has denied accusations that he must face 'full responsibility' for the abuse scandal in a German choir school revealed this week.

His comments came after it was revealed that more than 500 boys in a Church choir school were abused over a period of six decades.

A report found that at least 547 at the Regensburger Domspatzen ('Cathedral Sparrows') boys choir in Bavaria faced physical or sexual abuse in conditions likened to 'prison, hell and a concentration camp' between 1945 and 1992.

The lawyer leading the investigation into the abuse, Ulrich Weber, said that a 'culture of silence' had enabled the abuse to stay hidden, and accused Mueller of mishandling the abuse cases.

Cardinal Gerhard Ludwig Mueller, former bishop of Regensburg (2002 to 2012) and ex-prefect of the Vatican's Congregation for the Doctrine of Faith told the Italian daily Il Corriere della Sera that he felt 'shame for what has happened in the Church', according to The Tablet.

However, he added that 'everything that was possible and necessary was done'. He said that the abuse had taken place five decades before his 'mandate as bishop' began and insisted that he 'never defended' the choir school, and had set up his own investigation into it while bishop.

In response, the German government's abuse commissioner, Johannes-Wilhelm Rörig, said on July 20 that Mueller had again 'missed the chance' to respond with due compassion to the choir abuse scandal, and called for more 'appreciation and recognition' on Mueller's part.

Mueller responded that he saw no need to apologise since he himself had initiated the investigation that began in 2010.

Mueller was replaced as the Vatican's doctrinal chief at the beginning of this month. Reports suggested conservative Mueller had been at odds with a reforming Pope Francis for many years, particualrly on the issue of clerical sex abuse, though he denied claims of such intense division.