Pope Benedict, then called Josef Ratzinger, held the position from 1977 to 1982. He has denied the accusations.
But a new report into historical abuse allegations carried out by a German law firm incriminated the former pontiff.
Abuse continued under his tenure, it is alleged, and the accused priests remained active in church roles.
The former pope, now aged 94, became the first Church leader to resign in more than 600 years in 2013, citing exhaustion. Since then, he has led a largely quiet life in the Vatican City and is known as pope emeritus.