Mormon leaders have decreed that children of same-sex couples cannot be given a name or even blessed.

The Church of Jesus Christ of Latter-day Saints has updated its handbook to says children living in a same-sex household may not be blessed or baptised as babies. They cannot officially belong to the church until they are 18 years old and can leave and disown their parents, and even then they will have to get permission from the senior church leadership if they wish to be baptised. 

The new policy is significant because Mormons believe baptism is essential for salvation. Children are normally baptised around the age of eight. The church practices proxy baptism because of its belief that the souls of the dead can be saved in this way also.  

The handbook has been updated also to add same-sex marriage to its definitions of apostasy.

The decision, reported by Salt Lake City's KUTV,  takes effect immediately, according to church spokesman Eric Hawkins.

The policy says: "A natural or adopted child of a parent living in a same-gender relationship, whether the couple is married or cohabiting, may not receive a name and a blessing."

The changes were approved by the church's Council of the First Presidency and the Quorum of the Twelve Apostles.

The handbook now says: "A natural or adopted child of a parent living in a same-gender relationship, whether the couple is married or cohabiting, may be baptised and confirmed, ordained, or recommended for missionary service only as follows: A mission president or a stake president may request approval from the Office of the First Presidency to baptise and confirm, ordain, or recommend missionary service for a child of a parent who has lived or is living in a same-gender relationship when he is satisfied by personal interviews that both of the following requirements are met: 1. The child accepts and is committed to live the teachings and doctrine of the Church, and specifically disavows the practice of same-gender cohabitation and marriage. 2. The child is of legal age and does not live with a parent who has lived or currently lives in a same-gender cohabitation relationship or marriage."

Homosexual relations have been added to the church's list of "serious transgressions" in the disciplinary handbook. 

And mandatory disciplinary action is decreed for apostasy which now includes being "in a same-gender marriage".

Hawkins said in a statement: "Church handbooks are policy and procedural guides for lay leaders who must administer the church in many varied circumstances throughout the world. The church has long been on record as opposing same-sex marriages. While it respects the law of the land, and acknowledges the right of others to think and act differently, it does not perform or accept same-sex marriages within its membership."

The decision to change the handbook follows the US Supreme Court ruling earlier this year that same-sex marriage is a legal right.

It comes just days after Salt Lake City elected its first openly-gay mayor. As religious groups, Jehovah's Witnesses and Mormons are the most opposed to same-sex marriage. According to a recent Pew Research report, seven in ten Mormons oppose same-sex marriage, one of the highest levels of opposition for any religious group.

Dr John Dehlin, excommunicated from the church earlier this year, who did his PhD at Utah State university on the experiences of gay, lesbian, bisexual, and transgender Mormons and founded of the Mormon Stories website, wrote on Facebook: "This is a very sad day for Mormonism. It is sad for the many legally married LGBT Mormons will now likely be hunted down and threatened with the inhumane and barbaric LDS disciplinary council process - for the sole act of legally entering into a loving, committed relationship with a person of their choosing.

"It is sad for single LGBT Mormons who continue to receive an onslaught of invalidating religious messages (supposedly from God/Christ), leading to continued hopelessness, depression and despair - and that they are forced to choose between their faith, and a life of committed and loving companionship. No one should be forced to choose between their faith and loving companionship.

"And finally, it is sad for the LDS church and its devout members - who continue to deprive themselves of the wonderful talents and association with so many beautiful and gifted LGBT members.

"We are all diminished by this unfortunate action. As the LDS church continues to paint itself into a corner, it risks becoming increasingly irrelevant to the developed world. Perhaps this is for the best. We shall see."