The pope's apostolic letter on the "service of charity," issued "motu proprio" (on his own initiative), directs bishops in overseeing charitable works in their dioceses. The document, dated Nov. 11, was released by the Vatican Dec. 1.

Charities approved by the church or supported by church funds "are required to follow Catholic principles in their activity and they may not accept commitments which could in any way affect the observance of those principles," the pope wrote.

The staff members of such charities must therefore "share, or at least respect, the Catholic identity" of their agencies, and exemplify "Christian life" and faith. Bishops are to provide these employees with "theological and pastoral formation" through special courses and "suitable aids to the spiritual life."

Catholic charities are forbidden to "receive financial support from groups or institutions that pursue ends contrary to the church's teaching," or to "accept contributions for initiatives whose ends, or the means used to pursue them, are not in conformity with the church's teaching."

To ensure that the church's charitable agencies reflect "Christian simplicity of life," each bishop is to set their salaries and expenses at levels "in due proportion to analogous expenses of his diocesan curia."

When "the activity of a particular charitable agency is no longer being carried out in conformity with the church's teaching," Pope Benedict wrote, the responsible bishop must inform his flock and "prohibit that agency from using the name 'Catholic.'"

The document is the Vatican's latest measure aimed at reinforcing the religious identity of Catholic institutions. In May 2012, the Vatican issued rules strengthening its control over Caritas Internationalis, a confederation of 164 Catholic relief, development and social service agencies around the world, including Catholic Relief Services in the United States.

In the apostolic letter, the pope praised Caritas for its "generous and consistent witness of faith and its concrete ability to respond to the needs of the poor."

He also instructed bishops to foster the establishment of a "local Caritas service or a similar body" in every parish under their authority, not to only to provide aid to the needy but to educate the community in a "spirit of sharing and authentic charity."

Pope Benedict specified that the Pontifical Council Cor Unum, the Vatican office in charge of coordinating and promoting charitable giving, would be primarily responsible for "promoting the application of this legislation and ensuring that it is applied at all levels."