The Catholic Church in England and Wales has said gay people may make good parents but must still be banned from marriage.
Bishops have outlined their reasons why they believe same-sex couples should not be allowed to get married.
In the document published in the Catholic Herald, it states: ‘We recognize that many same-sex couples raise children in loving and caring homes.
‘Nevertheless, marriage has an identity that at its core is distinct from any other legally recognised relationship, no matter how much love or commitment may be involved in these other relationships.
‘Marriage has, over the centuries, been the enduring public recognition of this commitment to provide a stable institution for the care and protection of children, and it has rightly been recognised as unique and worthy of legal protection for this reason.
‘Marriage furthers the common good of society because it promotes a unique relationship within which children are conceived, born and reared, an institution that we believe benefits children.’
The bishops also say refusing marriage to same-sex couples is not discriminatory, as gay couples already have civil partnerships.
Despite the differences between civil partnerships and marriages, they say ‘it is not unequal or unfair to treat those in different circumstances differently.’
‘Catholic teaching, whilst it does not condone same sex sexual activity, condemns unfair discrimination on the basis of sexual orientation,’ they add.
‘Our opposition to same-sex marriage is not based in discrimination or prejudice; it is based in a positive effort to ensure that the unique social values currently served by marriage carry on being served by that institution in the future.’
The bishops also warn of a ‘slippery slope’, saying when civil partnerships were introduced in 2004, politicians promised same-sex marriage would not follow.
The Catholic Church now fears it is more likely marriage will be altered more in the coming years.
On 5 February, the UK government will have its first vote on marriage equality.