The Vatican has said the Catholic church cannot bless same-sex unions, as God “does not bless sin”.
In October, Pope Francis said in a documentary that he thought same-sex couples should be allowed to have "civil unions".
However, the Congregation for the Doctrine of the Faith (CDF), published a decree saying that such blessings “cannot be considered licit”.
While the decree said “the Christian community and its pastors must welcome with respect and sensitivity persons with homosexual inclinations”, their unions cannot be blessed.
On Monday, Pope Francis approved the response by the CDF, saying it was "not intended to be a form of unjust discrimination, but rather a reminder of the truth of the liturgical rite".
Some parishes in recent months, including in Germany and the US, have started giving blessings to people in same-sex relationships as a way to welcome gay Catholics to the church, it has been reported.
According to Catholic teaching, marriage between a man and a woman is part of God’s plan and intended for the creation of children. Since gay unions are not intended to be part of that plan, such relationships cannot be legitimately blessed.
The document went on to say that “God does not and cannot bless sin”, adding: “He blesses sinful man, so that he may recognise that he is part of his plan of love and allow him to be changed by him.”
Since he was elected pope in March 2013, Francis has sought to adopt a more inclusive tone towards LGBT people in his public statements.
Soon after becoming pope, he said in response to a question about gay priests: “Who am I to judge?”
Last year the pontiff said in a documentary by Evgeny Afineevsky that "homosexual people have a right to be in a family... they are children of God and have a right to a family. Nobody should be thrown out or made miserable over it".But his comments related to the civil domain and not within the Catholic church.