Catholics are being urged to protect the 'true meaning' of matrimony as the Catholic Church steps up its campaign against Government plans for gay marriage. Here is the full text of the letter to be read out in churches from two senior archbishops:
"Changing the legal definition of marriage would be a profoundly radical step.
Its consequences should be taken seriously now.
The law helps to shape and form social and cultural values.
A change in the law would gradually and inevitably transform society's understanding of the purpose of marriage.
It would reduce it just to the commitment of the two people involved.
There would be no recognition of the complementarity of male and female or that marriage is intended for the procreation and education of children.
We have a duty to married people today, and to those who come after us, to do all we can to ensure that the true meaning of marriage is not lost for future generations.
Neither the Church nor the State has the power to change this fundamental understanding of marriage itself.
The reasons given by our government for wanting to change the definition of marriage are those of equality and discrimination.
But our present law does not discriminate unjustly when it requires both a man and a woman for marriage.
It simply recognises and protects the distinctive nature of marriage."