VATICAN CITY (REUTERS) - Pope Francis, in another step towards greater equality for women in the Roman Catholic Church, on Monday (Jan 11) changed its law to formally allow them to serve as readers at liturgies, altar servers and distributors of communion.

In a decree, the Pope formalised what already has been happening in many developed countries for years.

But by introducing the change in the Code of Canon Law, it will be impossible for conservative bishops to block women in their diocese from having those roles.

But the Vatican stressed that these roles were "essentially distinct from the ordained ministry", meaning that they should not be seen as an automatic precursor to women one day being allowed to be ordained priests.

"The pontiff, therefore, has established that women can accede to these ministries and they are attributed by a liturgical function that institutionalises them," the Vatican said in an explanatory note.

In the decree, called Spiritus Domini (The Spirit of the Lord), Pope Francis said he had taken his decision after theological reflection.

He said many bishops from around the world had said that the change was necessary to respond to the "needs of the times".

In an accompanying letter, the pope said he wanted to bring "stability, public recognition" to women already serving in the roles.

"This shift bring the institutional Church in alignment with the pastoral realities around the world," said Ms Kate McElwee, executive director of the Women's Ordination Conference, which promotes a female priesthood.

In a big shift last August the pope appointed six women, including the former treasurer for Britain's Prince Charles, to senior roles in the council that oversees Vatican finances.

Pope Francis has already appointed women as deputy foreign minister, director of the Vatican Museums, and deputy head of the Vatican Press Office, as well as four women as councillors to the Synod of Bishops, which prepares major meetings.

He has also set up commissions to study the history of women deacons in the early centuries of the Catholic Church, responding to calls by women that they be allowed to take up the role today. Advocates of a female deaconate hope it could lead to women priests.

Deacons, like priests, are ordained ministers, and as in the priesthood, must be men in today's Church. They may not celebrate Mass, but they may preach, teach in the name of the Church, baptise and conduct wedding, wake and funeral services and even run a parish with the permission of a bishop.