Archbishop Mario Conti, of Glasgow, said new laws, such as potential legislation to allow same-sex marriages, were designed to "recreate society".
He said society will descend into "ethical confusion and moral disintegration the more those in Government and the judiciary slip society's moorings from the capstans of virtue".
In his sermon to mark the seventh anniversary of the election of Pope Benedict XVI, the archbishop said: "Those voices are growing ever louder in our country, that attempted marginalisation is becoming ever more acute and we are witnessing the transformation of tolerance into a kind of tyranny in which religious views are the only ones which seem unworthy of respect and acceptance."
He criticised politicians who "seem ready to redefine marriage without any reference to children, or to the natural law written on the heart of mankind, putting the claim of 'equality and diversity' on a higher level than faith and reason, and ultimately asserting the moral equivalence between marriage and same-sex unions."
He added: "Our society will descend further into ethical confusion and moral disintegration the more that those in Government and the judiciary slip society's moorings from the capstans of virtue."
The sermon was delivered at St Mary's Cathedral, Edinburgh, yesterday before all of Scotland's Catholic bishops and the Apostolic Nuncio to the UK, Archbishop Antonio Mennini.
Recently, Cardinal Keith O'Brien, leader of Scotland's Catholics, also launched an attack on gay marriage, describing it as an "aberration" that would send British society further into "immorality".
The UK Government is to launch a consultation on civil same-sex marriages and the Scottish Government has already completed a consultation and received more than 50,000 responses.
Its initial view was gay marriage "should be introduced but believes faith groups and their celebrants should not be obliged to solemnise same-sex marriages", adding: "If, as a result of the consultation, the Government decides to legislate, there will be a further consultation on a draft bill.
"A finalised bill could then be introduced into the Scottish Parliament in 2013."
Holyrood could legislate on the issue before Westminster – and it might mean the first major political battle over gay marriage could confront First Minister Alex Salmond rather than David Cameron.
Civil partnerships were introduced in 2005 to give homosexual couples the same legal rights as married couples, but the law does not allow such unions to be referred to as marriages.
Yesterday, the archbishop said the role of law in society has been to "defend the inalienable rights of its citizens; to ensure appropriate regulations for the management of the economy; to ensure that the sick and the poor are cared for; to provide universal education and so forth."
However he added: "It is certainly not the role of law to recreate our society according to passing fashions and ideologies, nor to redefine nature whether in terms of persons and their rights or its natural institutions."