Their fear is that Catholics who believe in the traditional meaning of marriage would effectively be excluded from some jobs – in the same way as Catholics were barred from many professions from the Reformation until the 19th century.

It said: “After centuries of persecution, Catholics have, in recent times, been able to be members of the professions and participate fully in the life of this country.

“Legislation for same-sex marriage, should it be enacted, will have many legal consequences, severely restricting the ability of Catholics to teach the truth about marriage in their schools, charitable institutions or places of worship.

“It is meaningless to argue that Catholics and others may still teach their beliefs about marriage in schools and other arenas if they are also expected to uphold the opposite view at the same time.”