The Vatican has ruled against transgender people becoming godparents because they live in breach of Church teaching.

Bishop Rafael Zornoza Boy of Cádiz and Ceuta in Spain had asked the Vatican for advice after a transgender man in his diocese requested to be the godfather to his nephew. Alex Salinas, 21, is a Catholic, and born a woman but identifies as a man.

In a statement posted to his diocesan website, Bishop Rafael said there was "confusion among some of the faithful" regarding the Church's teaching, and referred to "the complexity and media attention garnered by this issue". He therefore sought the guidance of the Congregation for the Doctrine of the Faith.

The Vatican ruled that transgender people could not become godparents due to "an attitude opposite to the moral imperative of solving the problem of sexual identity according to the truth of one's sexuality".

"It is evident that this person does not possess the requirement of leading a life according to the faith and to the position of godfather and is therefore unable to admitted to the position of godfather or godmother," the Vatican's response added.

"Discrimination is not to be seen in this, but only recognition of an objective lack of the requisites that by their own nature are necessary to take over the ecclesial responsibility of being a godparent."

Bishop Rafael has expressed his support for the decision. "The Church welcomes all persons charitably, wanting to help each one in their situation with sentiments of mercy, but without denying the truth that she preaches, proposed to all as a path a faith to be freely embraced," he said.

According to Catholic news website Crux, Salinas' priest had originally agreed to his becoming godfather, and the 21-year-old has denounced the Church's reversal.

In a Facebook post, Salinas said: "Just don't have words for all this I'm feeling. Disgust, anger, sadness...I feel so cheated".

He said he will no longer be part of the Church, and his family has now chosen not to baptise the child.

It is generally agreed that the Catholic Church has shifted its attitude towards LGBT Catholics since Pope Francis took office. The pope has met with transgender and gay people and is widely considered to have adopted a more gentle tone than his predecessors, but his encyclical on the environment released in June this year has been criticised by LGBT activists for placing emphasis on the importance of gender differences.

"The acceptance of our bodies as God's gift is vital for welcoming and accepting the entire world as a gift from the Father and our common home, whereas thinking that we enjoy absolute power over our own bodies turns, often subtly, into thinking that we enjoy absolute power over creation," Francis wrote.

"Learning to accept our body, to care for it and to respect its fullest meaning, is an essential element of any genuine human ecology. Also, valuing one's own body in its femininity or masculinity is necessary if I'm going to be able to recognise myself in an encounter with someone who is different...It is not a healthy attitude which would seek to cancel out sexual difference because it no longer knows how to confront it."