Vatican city (REUTERS) - Pope Francis on Wednesday approved an unprecedented Vatican department to judge bishops accused of covering up or not preventing sexual abuse of minors, meeting a key demand by victims' groups.

A statement said the department would come under the auspices of the Congregation for the Doctrine of the Faith, the Vatican's doctrinal arm, "to judge bishops with regard to crimes of the abuse of office when connected to the abuse of minors".

Victims groups have for years been urging the Vatican to establish clear procedures to make bishops more accountable for abuse in their dioceses, even if they were not directly responsible for it.

Vatican spokesman Father Federico Lombardi told reporters that the bishops could also be judged if they had failed to take measures to prevent sexual abuse of minors.

The complaints against the bishops would be initially investigated by one of three Vatican departments, depending on under whose jurisdiction the bishops fall, before being judged by the doctrinal department.

The Vatican said the pope had approved proposals made to him by a commission advising him on how to root out sexual abuse of children.

Part of the task of the commission, which is made up of 17 clerics and lay people from around the world, is to help dioceses put in place "best practices" to prevent abuse and work with victims in a process of healing. Eight members are women.

The worldwide scandal, which first became prominent in Boston in 2002, has seen known abusers shunted from parish to parish instead of being defrocked and handed over to authorities.

Last February, Francis ordered bishops the world over to cooperate as a matter of priority with the commission to root out "the scourge" of the sexual abuse even if it unearths new scandals.