Gay marriage would be 'disastrous', says Archbishop
11 March 2012 Last updated at 08:52 GMT
The Roman Catholic Church in England and Wales is stepping up its campaign against the government's plan to legalise same-sex marriage.
In a letter being read in thousands of parish churches, the two most senior archbishops say the change would reduce the significance of marriage, and that Catholics have a duty to make sure it doesn't happen.
Archbishop Peter Smith told the BBC a married couple and their children "forms the basic building block of a healthy society".